Personal H. Soliman G. Tsirtsis Flarion Internet Draft Document: draft-soliman-v4v6-mipv6-00.txt Category: Standards Track March 2004 Expires: September 2004 Dual Stack Mobile IPv6 draft-soliman-v4v6-mipv6-00.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026 [1]. 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. Abstract This specification adds IPv4 extensions to Mobile IPv6 to allow dual stack mobile nodes to roam within the Internet using Mobile IPv6 only while simultaneously maintaining connections using their IPv4 and IPv6 home addresses. 1 <2003> Table of Contents 1. Introduction.......................................................2 1.1 Why Mobile IPv6 only?.............................................2 2. Solution overview..................................................3 2.1. Dynamic Home Agent Address Discovery.............................3 2.2. Binding management...............................................4 2.2.1 Visited network supports IPv6...................................4 2.2.2 Visited network supports IPv4 only (public addresses)...........5 2.3. Route optimization...............................................5 2.4. Dynamic IPv4 home address allocation.............................6 3. Extensions and modifications to Mobile IPv6........................6 3.1. Binding update extensions........................................6 3.1.1 IPv4 home address option........................................6 3.2. Binding acknowledgement extensions...............................6 3.2.1 IPv4 address acknowledgement option.............................7 3.3. Mobile node operation............................................7 3.4. Home agent operations............................................9 3.5. Correspondent node operations...................................10 4. Security considerations...........................................10 5. References........................................................10 Author's Addresses...................................................11 1. Introduction Mobile IPv6 allows mobile nodes to move within the Internet while maintaining reachability and ongoing sessions, using an IPv6 home address. However, since IPv6 is not widely deployed, it is unlikely that mobile nodes will use IPv6 addresses only for their connections. It is reasonable to assume that mobile nodes will, for a long time, need an IPv4 home address that can be used by upper layers. The current Mobile IPv6 specification does not allow mobile nodes to use an IPv4 home address. Hence, this specification extends Mobile IPv6 capabilities to allow dual stack mobile nodes to request that their home agent (also dual stacked) tunnel IPv4/IPv6 packets addressed to their home addresses, to their IPv4/IPv6 care-of address(es). As a result, mobile nodes only need Mobile IPv6 to manage mobility while moving within the Internet. This specification provides the extensions needed in order to allow Mobile IPv6 only to be used by dual sack mobile nodes. 1.1 Why Mobile IPv6 only? IPv6 offers a number of improvements over today’s IPv4, primarily due to its large address space. Mobile IPv6 offers a number of improvements over Mobile IPv4, mainly due to capabilities inherited from IPv6. For instance, route optimization and Dynamic home agent discovery can only be achieved with Mobile IPv6. 2 <2003> One of the advantages of the large address space provided by IPv6 is that it allows mobile nodes to obtain a global care-of address wherever they are. Hence, there is no need for NAT traversal techniques designed for Mobile IPv4. This allows Mobile IPv6 to be a significantly simpler and more bandwidth efficient mobility management protocol. All of the above benefits make the case for using Mobile IPv6 only for dual stack mobile nodes. 2. Solution overview In order to allow Mobile IPv6 to be used by dual stack mobile nodes, the following needs to be done: - Mobile nodes should be able to use an IPv4 and IPv6 home or care- of address simultaneously and update their home agents accordingly. - Mobile nodes need to be able to know the IPv4 address of the home agent as well as its IPv6 address. There is no need for IPv4 prefix discovery however. This section presents an overview of the extensions required in order to allow mobile nodes to use Mobile IPv6 only for IP mobility management. 2.1. Dynamic Home Agent Address Discovery Mobile IPv6 allows mobile nodes to discover their home agents by appending a well-known anycast interface identifier to their home link’s prefix. The mobile node sends a Mobile Prefix solicitation and receives a Mobile Prefix Advertisement containing all prefixes advertised on the home link. To allow mobile nodes to use an IPv4 home address they need to be configured with the home agent’s IPv4 address and possibly with the IPv4 home address. A dual stack mobile node MAY send a Mobile Prefix Solicitation message encapsulated in IPv4 (i.e. IPv6 in IPv4) in the case where the mobile node has no access to IPv6 within the local network. Securing such messages would require the mobile node to have security association with the home agent, using IPsec (AH or ESP) and based on the mobile node’s IPv4 care-of address. However, since the mobile node needs to encapsulate all IPv6 traffic into IPv4, while located in an IPv4-only visited network, such SA would affect all packets. That is, the SA selectors being the protocol number (protocol is always IP in IP), as well as, source and destination addresses are all common to all packets. Therefore, it is RECOMMENDED that the mobile node does not use Dynamic Home Agent Address Discovery when located in an IPv4-only network. From the above discussion, it is clear that the mobile node will need to be configured with its home agent addresses (IPv4 and IPv6) and its home addresses. 3 <2003> 2.2. Binding management A dual stack mobile node will need to update its home agent with its care-of address. If a mobile node has an IPv4 and an IPv6 home address it will need to create a binding cache entry for each address. The format of the IP packet carrying the binding update and acknowledgement messages will vary depending on whether the mobile node has access to IPv6 in the visited network. There are three different scenarios to consider with respect to the visited network: A. The visited network has IPv6 connectivity and provides the mobile node with a care-of address (in a stateful or stateless manner), in addition to IPv4 addresses (public or private). B. The mobile node can only configure a globally unique IPv4 address in the visited network. C. The mobile node can only configure a private IPv4 address in the visited network. This specification is only concerned with cases A and B. Case C is not supported by this specification. Case C can be supported if the visited network provided IPv6 service, e.g. by introducing an ISATAP router that provides global IPv6 connectivity. Binding management in cases A and B is considered in the following sections. 2.2.1 Visited network supports IPv6 In this case, the mobile node is able to configure a globally unique IPv6 address. The mobile node will send a binding update to the IPv6 address of its home agent, as defined in [1]. The binding update will include the IPv4 home address option introduced in this document. After receiving the binding update, the home agent creates two binding cache entries, one for the mobile node’s IPv4 home address, and another for the mobile node’s IPv6 home address. Both entries will point to the mobile node’s IPv6 care-of address. Hence, whenever a packet is addressed to the mobile node’s IPv4 or IPv6 home addresses, it will be tunneled in IPv6 to the mobile node’s IPv6 care-of address included in the binding update. Effectively, the mobile node establishes two different tunnels, one for its IPv4 traffic (IPv4 in IPv6) and one for its IPv6 traffic (IPv6 in IPv6) with a single binding update. The security implications of this mechanism are discussed in the security considerations section. In this scenario, the only addition to [MIPv6] is the inclusion of the IPv4 home address option in the binding update message. After accepting the binding update and creating the corresponding binding cache entries, the home agent MUST send a binding acknowledgement to the mobile node as defined in [MIPv6]. In addition, if the binding update included an IPv4 home address option, the binding acknowledgement MUST include the IPv4 address acknowledgment option as described later in this specification. This 4 <2003> option informs the mobile node whether the binding was accepted for the IPv4 home address. If this option is not included in the binding acknowledgement and the IPv4 home address option was included in the binding update, the mobile node MUST assume that the home agent does not support the IPv4 home address option and therefore SHOULD NOT include the option in future binding updates to that home agent address. The routing header in the binding update MUST include the mobile node’s IPv6 home address as specified in [MIPv6]. 2.2.2 Visited network supports IPv4 only (public addresses) In this scenario the mobile node will need to tunnel IPv6 packets containing the binding update to the home agent’s IPv4 address. The mobile node uses the IPv4 address it gets from the visited network as a source address in the outer header. The binding update will contain the mobile node’s IPv6 home address in the home address option. However, since the care-of address in this scenario is the mobile node’s IPv4 address, the mobile node MUST include its IPv4 care-of address in the IPv6 packet. The IPv4 address is represented in an IPv4-mapped IPv6 address and is included in the source address field of the IPv6 header. If the mobile node had an IPv4 home address, it MUST also include the IPv4 home address option described in this specification. After accepting the binding update, the home agent MUST create a new binding cache entry for the mobile node’s IPv6 home address. If an IPv4 home address option were included, the home agent MUST create another entry for that address. All entries MUST point to the mobile node’s IPv4 care-of address. Hence, all packets addressed to the mobile node’s home address(es) (IPv4 or IPv6) will be encapsulated in an IPv4 header that includes the home agent’s IPv4 address in the source address field and the mobile node’s IPv4 care-of address in the destination address field. After accepting the binding updates and creating the corresponding entries, the home agent MUST send a binding acknowledgement as specified in [MIPv6]. In addition, if the binding update included an IPv4 home address option, the binding acknowledgement MUST include the IPv4 address acknowledgment option as described later in this specification. The binding update is encapsulated to the IPv4 care- of address (represented as an IPv4-mapped IPv6 address in the binding update). 2.3. Route optimization Route optimization, as specified in [MIPv6] will operate in an identical manner for dual stack mobile nodes when they are located in a visited network that provides IPv6 addresses to the mobile node. However, when located in an IPv4-only network, route 5 <2003> optimization will not be possible. Therefore, mobile nodes will need to communicate through the home agent. Route optimization will not be possible for IPv4 traffic. That is, traffic addressed to the mobile node’s IPv4 home address. This is similar to using Mobile IPv4, therefore there is no reduction of features resulting from using this specification. 2.4. Dynamic IPv4 home address allocation It is possible to allow for the mobile node’s IPv4 home address to be allocated dynamically. This is done by including 0.0.0.0 in the IPv4 home address option included in the binding update. The home agent SHOULD allocate an IPv4 address to the mobile node and include it in the IPv4 address acknowledgement option sent to the mobile node. In this case, the lifetime of the binding is bound to the minimum of the lifetimes of the IPv6 binding and the lease time of the IPv4 home address. 3. Extensions and modifications to Mobile IPv6 This section highlights the protocol and implementation additions required to support this specification. 3.1. Binding update extensions 3.1.1 IPv4 home address option This option is included in the Mobility Header including the binding update message sent from the mobile node to a home agent or Mobility Anchor Point. 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv4 home address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type TBD Length 1 IPv4 home address The mobile node’s IPv4 home address that should be defended by the home agent. This field could contain any unicast IPv4 address (public or private) that was assigned to the mobile node. The value 0.0.0.0 is used to request an IPv4 home address from the home agent. 3.2. Binding acknowledgement extensions 6 <2003> 3.2.1 IPv4 address acknowledgement option This option is included in the Mobility Header including the binding acknowledgement message sent from the home agent or Mobility Anchor Point to the mobile node. This option indicates whether a binding cache entry was created for the mobile node’s IPv4 address. Additionally, this option can include an IPv4 home address in case the mobile node was not configured with one (i.e. if the unspecified IPv4 address was included in the 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Status |Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv4 home address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type TBD Length 1 Status Indicates success or failure for the IPv4 home address binding. Values from 0 to 127 indicate success. Higher values indicate failure. The following values are reserved: 0 Success 128 Failure, reason unspecified 129 Administratively prohibited 130 Incorrect IPv4 home address 131 Invalid IPv4 address 132 Dynamic IPv4 home address assignment not available IPv4 home address The IPv4 home address that the home agent will use in the binding cache entry. This could be a public or private address. This field MUST always contain the mobile node’s IPv4 address. If the address were dynamically allocated the home agent will add the address to inform the mobile node. Otherwise, if the address were statically allocated to the mobile node, the home agent will copy it from the binding update message. 3.3. Mobile node operation In addition to the operations specified in [MIPv6], this specification requires mobile nodes to be able to support an IPv4 home address. The IPv4 home address is never sent in the IPv4-mapped IPv6 address format. This is primarily done to save bandwidth. However, to simplify the mobile node’s implementation, they SHOULD store the IPv4 home address in the binding update list, using the 7 <2003> IPv4-mapped IPv6 format. Mobile nodes are also required to be configured with the home agent’s global IPv4 address. When sending an IPv6 packet containing a binding update while connected to an IPv4-only access network, mobile nodes MUST ensure the following: - The IPv6 packet is encapsulated in an IPv4 packet - The source address in the IPv4 header is the mobile node’s IPv4 care-of address - The destination address in the IPv4 header is the home agent’s IPv4 address. - The source address in the IPv6 header is the mobile node’s IPv4- mapped IPv6 address. That is, the same IPv4 address in the outer header is placed in the IPv6 header using the mapped address format. - The home address option contains the IPv6 home address as specified in [MIPv6]. - The IPv4 home address option MAY be included in the mobility header. This option contains the IPv4 home address. If the mobile node did not have a static home address it MAY include the unspecified IPv4 address, which acts as a request for a dynamic IPv4 home address. - The IPv6 packet MUST be authenticated as per [MIPv6], based on the mobile node’s IPv6 home address. When sending a binding update from a visited network that supports IPv6, the mobile node MUST follow the rules specified in [MIPv6]. In addition, if the mobile node has an IPv4 home address or needs one, it should include the IPv4 home address option in the mobility header. If the mobile node already has a static IPv4 home address, such address MUST be included in the IPv4 home address option. Otherwise, if the mobile node needs a dynamic IPv4 address, it should include the IPv4 unspecified address in the IPv4 home address option. When the mobile node receives a binding acknowledgement from the home agent, it should follow the rules in [MIPv6]. In addition, the following actions MUST be made: - If the mobility header includes and IPv4 address acknowledgement option indicating success, the mobile node should create two entries in its binding update list, one for the IPv6 home address and another for the IPv4 home address. - If no IPv4 address acknowledgement option were present, and an IPv4 home address option was present in the binding update, the mobile node MUST only create one binding update list entry for its IPv6 home address. The mobile node MAY include the IPv4 home address option in future binding updates. - If an IPv4 address acknowledgement option were present and it indicates failure for the IPv4 home address binding, the mobile node MUST NOT create an entry for that address in its binding update list. The mobile node MAY include the IPv4 home address 8 <2003> option in future binding updates. Note that a mobile node complying with this specification MUST configure an IPv4-mapped IPv6 address on its interface in the visited network. This is needed in order to allow the mobile node to receive binding acknowledgements from its home agent while located in an IPv4-only network. 3.4. Home agent operations In addition to the home agent specification in [MIPv6], the home agent needs to be able to process the IPv4 home address option and generate the IPv4 address acknowledgement option. Both options are included in the mobility header. In order to comply with this specification, the home agent MUST be able to find the IPv4 home address of a mobile node when given the IPv6 home address. That is, given an IPv6 home address, the home agent MUST store the corresponding IPv4 home address if a static one is present. If a dynamic address were requested by the mobile node, the home agent MUST store that address (associated with the IPv6 home address) after it’s allocated to the mobile node. When the home agent receives a binding update containing the IPv4 home address option, it needs to follow all the steps in [MIPv6], in addition, the following checks MUST be done: - If the IPv4 home address option contains a valid unicast IPv4 address, the home agent MUST check that this address is allocated to the mobile node that has the IPv6 home address included in the home address option. - If the IPv4 home address option contained the unspecified IPv4 address, the home agent SHOULD dynamically allocate and IPv4 home address to the mobile node. If none is available, the home agent MUST return an appropriate error code in the status field of the IPv4 address acknowledgement option. - If the binding update is accepted for the IPv4 home address, the home agent MUST create a binding cache entry for the IPv4 home address. The IPv4 home address MAY be stored in the IPv4-mapped IPv6 address format. The home agent MUST include an IPv4 acknowledgement option in the mobility header containing the binding acknowledgement. If the binding update is accepted for both IPv4 and IPv6 home addresses, the home agent MUST create two separate binding cache entries, on for each home address. The care-of address is the one included in the binding update. If the care-of address is an IPv4- mapped IPv6 address, the home agent MUST setup a tunnel to the IPv4 care-of address of the mobile node. 9 <2003> When sending a binding acknowledgement to the mobile node, the home agent would construct the message according to [MIPv6]. Note that the routing header MUST always contain the IPv6 home address as specified in [MIPv6]. If the care-of address of the mobile node were an IPv4 address, the home agent MUST include this address in the destination address in the IPv6 header using the IPv4-mapped IPv6 format. The home agent MUST then encapsulate the packet in an IPv4 header. The source address is set to the home agent’s IPv4 address and the destination address is set to the mobile node’s IPv4 care-of address. After creating a binding cache entry for the mobile node’s home addresses. All packets sent to the mobile node’s home addresses are tunneled by the home agent to the mobile node’s care-of address. If the care-of address is an IPv4 address, packets are encapsulated in an IPv4 header. Note that the mapped address format is not used to encapsulate the mobile node’s traffic. The mapped address format is only used when sending binding acknowledgements to the mobile node. 3.5. Correspondent node operations The specification has no impact on IPv4 or IPv6 correspondent nodes. 4. Security considerations This specification allows a mobile node to send one binding update for its IPv6 and its IPv4 home address. This is a slight deviation from [MIPv6] which requires one binding update per home address. However, like [MIPv6], the IPsec security association needed to authenticate the binding update is till based on the mobile node’s IPv6 home address. Therefore, in order to authenticate the mobile node’s IPv4 home address binding, the home agent MUST store the IPv4 address corresponding to the IPv6 address that is allocated to a mobile node. Therefore, it is sufficient for the home agent to know that the IPsec verification for the packet containing the binding update was valid provided that it knows which IPv4 home address is associated with which IPv6 home address. Hence, the security of the IPv4 home address binding is the same as the IPv6 binding. In effect, associating the mobile node’s IPv4 home address with its IPv6 home address moves the authorization of the binding update for the IPv4 address to the Mobile IPv6 implementation, which infers it from the fact that mobile node has an IPv6 home address and the right credentials for sending an authentic binding update for such address. 5. References [IPv6] S. Deering and B. Hinden, “Internet Protocol version 6 (IPv6) specification”, RFC 2460 [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate 10 <2003> Requirement Levels", BCP 14, RFC 2119, March 1997. [MIPv4] C. Perkins, "Mobility Support for IPv4", RFC3344 [MIPv6] D. Johnson, C. Perkins and J. Arkko, "Mobility Support in IPv6", draft-ietf-mobileip-ipv6-24.txt, June 2003. Author's Addresses Hesham Soliman Flarion Technologies Phone: +61400500321 E-mail: H.Soliman@Flarion.com George Tsirtsis Flarion Technologies Phone: +44-20-88260073 Email1: G.Tsirtsis@Flarion.com Email2: tsirtsisg@yahoo.com 11