Mobile IP Working Group Thierry Ernst INTERNET-DRAFT Ludovic Bellier Castelluccia Claude Hong-Yon Lach Motorola Labs, Paris and INRIA, France 14 July 2000 Mobile Networks Support in Mobile IPv6 draft-ernst-mobileip-v6-network-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. 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 draft addresses the problems of routing datagrams to nodes located in an IPv6 mobile network. A mobile network is a network that is changing its point of attachment dynamically such as a network deployed in an aircraft, a boat, or a car. Mobile IPv6 [4] has been developed to support mobile nodes and is unable to support mobile networks efficiently. This draft discusses the Mobile IPv6 ability to support mobile networks and proposes to extend Mobile IPv6 with prefix scope binding updates to support mobile networks in the Internet. All datagrams bearing a destination address which prefix matches a home network prefix recorded in the binding cache are routed to the corresponding care-of address. Ernst and Bellier Expires 14 January 2001 [Page 1] INTERNET-DRAFT Mobile Networks Support in Mobile-IPv6 14 July 2000 1. Introduction Mobile IPv4 [8] and Mobile IPv6 [4] have introduced mobility support for IPv4 and IPv6 [3] nodes respectively. The purpose of mobility support is to provide continuous Internet connectivity to mobile nodes. Mobile IP is a solution to support mobile nodes but does not handle mobile networks. There are situations where an entire network might move and attach to different places in the Internet topology. In this paper, we refer to a network as a set of nodes that share the same IP prefix and that are attached to the Internet through a single border router. We refer to a mobile network as a network whose border router is dynamically changing its point of attachment to the Internet and thus its reachability in the IP topology. The internal architecture of a mobile network is preserved while it is roaming. As such, nodes in the mobile network do not move with respect to the others and shouldn't take part in mobility management. Applications of mobile networks include networks attached to people (Personal Area Network or PANs) and networks of sensors deployed in aircrafts, boats, cars, trains, etc. As an example of a mobile network, we could imagine that an airways company provides permanent on-board Internet connectivity. This allows all passengers to use their laptops to connect to remote hosts, download music or video from any provider, or browse the web. The Internet could also be used to exchange information between the aircraft and air traffic control stations. During the flight, the aircraft changes its point of attachment to the Internet and is reachable by distinct IP addresses owned by distinct Internet service providers. This scenario justifies that mobile networks may be of a big size, containing hundreds of hosts and several routers and may attach to very distant parts of the Internet topology. Although the designers of Mobile IPv4 claim that it could support mobile networks equally as mobile nodes ([8] section 4.5, [9] section 5.12, [7] section 11.2), we argue that this is not true for Mobile IPv6, which therefore requires some changes in the specification. Indeed, we have carefully studied the adequacy of Mobile IPv6 for supporting mobile networks and we came to the conclusion that some modifications are needed to support them. 2. Terminology 2.1. General terms General terms are as defined in the Mobile IPv6 specification [4]. Ernst and Bellier Expires 14 January 2001 [Page 2] INTERNET-DRAFT Mobile Networks Support in Mobile-IPv6 14 July 2000 2.2. Mobile Network terms Network A set of nodes that share the same IP prefix and that are attached to the Internet through a single border router Mobile Network A network whose border router is dynamically changing its point of attachment to the Internet and thus its reachability in the IP topology. Mobile Router (MR) The border router of the mobile network which attaches the mobile network to the rest of the Internet. Foreign Gateways (FGs) Subsequent points of attachment of the mobile network Mobile Network Node (MNN) Any host or router located within the mobile network. Correspondent Node (CN) External nodes corresponding with one or more MNNs of the mobile network. Mobile Network Prefix A bit string that consists of some number of initial bits of the home address of a mobile router, i.e the network prefix that is shared by both the Mobile Router and all the Mobile Network Nodes when the Mobile Router is attached on the home link. Figure 1 illustrates a mobile network attached to its home link. In figure 2, the mobile network has moved and is attached to a foreign link. 2.3. Assumptions We make the assumption that the mobile network attaches to the Internet through only one mobile router and that this mobile router is not multihomed. We also make the assumptions that nodes in the mobile network do not move with respect to the mobile router and are configured with a common and unique mobile network prefix. ____ | | Ernst and Bellier Expires 14 January 2001 [Page 3] INTERNET-DRAFT Mobile Networks Support in Mobile-IPv6 14 July 2000 | CN | |____| ___|____________________ | | | | | Internet | | | |________________________| __|_ __|_ ____ | | Router | | | | | FG | | R | | HA | |____| |____| |____| _____|________|____ home Foreign __|_ link Gateway | | | MR | Mobile |____| Router _________|_____ __|__ __|__ | | | | Mobile | MNN | | MNN | Network |_____| |_____| Node Figure 1 : Mobile Network at home ____ | | | CN | |____| ___|____________________ | | | | | Internet | | | |________________________| __|_ __|_ ____ | | | | | | Home | FG | | R | | HA | Agent |____| |____| |____| _______|_____ ___|________|____ __|_ foreign | | link | MR | |____| _____|_______ __|__ __|__ | | | | | MNN | | MNN | Ernst and Bellier Expires 14 January 2001 [Page 4] INTERNET-DRAFT Mobile Networks Support in Mobile-IPv6 14 July 2000 |_____| |_____| Figure 2 : Mobile Network attached to a foreign link 3. Mobile IP and Mobile Networks 3.1 Review of Mobile IP and Mobile Networks From the routing perspective, distinction between nodes is only necessary for routing inside the network. From outside, a network can be virtually perceived as a single node (the mobile router MR) with one address (or prefix) and n interfaces attached to it. According to this observation, the Mobile IPv4 specification proposes to support mobile networks as standard mobile nodes (see [8] section 4.5, [9] section 5.12, [7] section 11.2). In this situation, the mobile node is the border router MR of the mobile network. It has a permanent home address on its home link and gets a new care-of address at each subsequent point of attachment. As any mobile node, it sends a Binding Update to its home agent HA to instruct it to intercept all datagrams intended for its MNNs. Mobile IPv6 and Mobile IPv4 with Routing Optimization [11] could in theory support mobile networks similarly as in Mobile IPv4. However, although mentioned in the Mobile IPv4 specification, the current specifications of Mobile IPv4 with Routing Optimization and Mobile IPv6 don't mention them anymore. 3.2. Inability of Mobile IPv6 to support mobile networks 3.2.1. Registration with the Home Agent Obtaining a care-of address and requesting the HA to redirect in flight datagrams intended for the MR doesn't require modifications in the Mobile IPv6 specification as this could be done independently for a host or for a router. However, although the HA is able to intercept datagrams intended to the MNNs, it is not able to encapsulate them to the care-of address of the Mobile Router. Once it receives a valid Binding Update, the Home Agent records in its Binding Cache the binding between the home address of the sender and its care-of address. The home address is used as the key for searching the Binding Cache ([4] section 4.6). Datagrams reaching the home link and destined to a MNN are intercepted Ernst and Bellier Expires 14 January 2001 [Page 5] INTERNET-DRAFT Mobile Networks Support in Mobile-IPv6 14 July 2000 by the Home Agent because it claims to be the Mobile Router, i.e. the next hop towards the MNN. Then, the Binding Cache is searched for the destination address contained in the received datagram. Unfortunately, at this point, the Home Agent is unable to find an entry since no binding bearing the destination address of the MNN is recorded in the Binding Cache. This is illustrated on figure 3 where CN sends a packet to MNN-1 (IP address FECA:700:AAAA:103C/64). MR (home address FEC4:700:AAAA:1020/64) has registered its primary care-of address (FEC4:700:BBBB:202A/64) with its HA. The Binding between the home address and the care-of address of MR is recorded in the Binding Cache. HA is therefore instructed to intercept all datagrams sent to MR. The packet reaches HA because MR is the next hop towards the destination MNN-1. HA searches its Binding Cache for an entry corresponding to destination address FECA:700:AAAA:103C/64 but does find any entry and drop the datagram. ____________________________________ | | | CN | | MNN-1: FECA:700:AAAA:103C:MNN-1_ID | |____________________________________| | _________________|_________________ | | | | | Internet | | | |___________________________________| | | | FECA:700:BBBB:2020/64 | FECA:700:AAAA:1010/64 __|__ ____________________|_________________________________ | | | | | FG | | HA | | | | Binding Cache: | | | | FEC4:700:AAAA:1020:MR_ID -> FEC4:700:BBBB:202A:MR_ID | |_____| |______________________________________________________| | | | FEC4:700:BBBB:202A/64 FEC4:700:AAAA:1020 | _|_________________________________________ | | | | MR | | Home address FEC4:700:AAAA:1020:MR_ID | | Care-of address FEC4:700:BBBB:202A:MR_ID | |___________________________________________| Ernst and Bellier Expires 14 January 2001 [Page 6] INTERNET-DRAFT Mobile Networks Support in Mobile-IPv6 14 July 2000 | | __|__ __________|__________________ | | | | | MNN | | MNN-1 | | | | FECA:700:AAAA:103C:MNN-1_ID | |_____| |_____________________________| Figure 3 : Packets destined to MNN-1 are dropped by Home Agent 3.2.2 Registration with Correspondent Nodes Regarding the emission of Binding Updates to CNs, it makes sense that the node which is assigned the care-of address also sends Binding Updates. As a result, the Mobile Router would have to send a Binding Update on behalf of its MNNs, which has the benefit of hiding mobility of the network to the MNNs and frees them from any mobility management. Doing so while keeping MNNs out of any mobility management requires that the Mobile Router tracks the CNs of the MNNs and sends them Binding Updates. Those datagrams require authentication. Piggybacking cannot be done by the Mobile Router without rewriting the AH or ESP header which may be present. Sending Binding Updates in separate datagrams requires that the Mobile Router uses the same security association as the MNN so that the CN accepts to send datagrams to the MNN via the careof-address of the Mobile Router. Both scenarios do not comply with IPv6 recommendations since no headers but the Routing extension (under some particular conditions) can be rewritten by routers along the path. We could think of mechanisms that would allow the Mobile Router to authenticate itself as one of its MNNs. But, although the Mobile Router and its MNNs are likely to trust each other and adopt the same administrative policy, it is not desirable to mislead the recipients since no node is authorized to send Binding Updates on behalf of a mobile node [4, section 10.8]. To avoid these constraints, we may nevertheless consider that MNNs directly send Binding Updates to their CNs. This solution requires a mechanism to distribute the care-of address of the Mobile Router to all MNNs. They would consequently take part in mobility management. This approach is quite advantageous since the process of sending and authenticating Binding Updates is left unchanged. Binding Updates could be piggybacked or sent alone and are authenticated as coming from the MNNs. On the other hand, it requires changes of the Mobile IPv6 mobile node operation as MNNs do not need to perform the tasks of obtaining a careof address and registering it with a Home Agent. Ernst and Bellier Expires 14 January 2001 [Page 7] INTERNET-DRAFT Mobile Networks Support in Mobile-IPv6 14 July 2000 As we can see, both approaches have drawbacks and necessitate changes in the Mobile IPv6 specification. We also note that CNs may be communicating with several MNNs located in the same mobile network. In this situation, they would redundantly record a binding containing the same care-of address for each MNN it is communicating with. 4. Mobile IPv6 enhancements to support mobile networks According to the observations made in section 3, we propose to enhance Mobile IPv6 with "prefix scope binding updates". Instead of establishing a one-to-one relationship between a home address and a care-of-address, the binding establishes a many-to-one relationship between the set of nodes that share the same mobile network prefix and a care-of-address. Prefix Scope Binding Updates are Binding Updates that associate a care-of address with the mobile network prefix instead of the full 128-bits IPv6 home address. The mobile network prefix is used as a netmask in the Binding Cache. The Binding Update instructs its recipients to use the care-of address of the mobile router for all packets which destination is one MNN. Note that each CN only receives one copy of the Binding Update even if it communicates with several MNNs located in the same mobile network. This is performed by means of a new flag and a mobile network prefix carried in Binding Updates and recorded in the Binding Cache. This only requires to redefine the procedure for searching the Binding Cache by both the Home Agent and the Correspondent Node. 4.1. Packet Format of the Binding Update The format of the Binding Update is the same as defined in [4] except the Binding Update Option. A new field "Prefix Scope Registration" is added and is taken from the "Reserved" field. In addition, the "Mobile Network Prefix" is a new sub-option that contains the mobile network prefix. 4.1.1. New Binding Update Option format The Binding Update option is encoded in type-length-value (TLV) format as follows: Ernst and Bellier Expires 14 January 2001 [Page 8] INTERNET-DRAFT Mobile Networks Support in Mobile-IPv6 14 July 2000 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |A|H|R|D|P|Rsrvd| Prefix Length | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-Options... +-+-+-+-+-+-+-+-+-+-+-+- Prefix Scope Registration (P) The Prefix Scope Registration (P) bit is set by the sending mobile node to request the receiving node to route all packets bearing a prefix (see section 4.1.2) set of initial bits in the destination address that matches the "Mobile Network Prefix" to the mobile router's careof address using a Routing Extension header. Rsrvd This field is reduced from a 4-bit field to a 3-bit field to account for the addition of the "Prefix Scope Registration" bit. The remaining 3 bits are unused and MUST be initialized to zero by the sender and MUST be ignored by the receiver. 4.1.2. Mobile Network Prefix Sub-Option 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Sub-Option Type| Sub-Option Len| Prefix Length | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + Mobile Network Prefix + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The Mobile Network Prefix Sub-Option is valid only in the Binding Update destination Option if the "Prefix Scope Registration" (P) bit is set. It is filled by the sending mobile node to request its Home Agent and its correspondent nodes to record a Prefix Scope entry in the Binding Cache (see section 4.2) Ernst and Bellier Expires 14 January 2001 [Page 9] INTERNET-DRAFT Mobile Networks Support in Mobile-IPv6 14 July 2000 The Prefix Length field is set to the (nonzero) length of the mobile network prefix. The Mobile Network Prefix field is set to the prefix of the mobile network. 4.2. Cache Management 4.2.1. Binding Cache entries Each Binding Cache entry contains the same fields as defined in [4]. However, the interpretation of the "Prefix Length" field is redefined and a new "Prefix Scope Registration" flag is added: - a flag "Prefix Scope Registration" indicating whether or not this Binding Cache entry represents a mobile router that is serving a mobile network. - the value of the "Prefix Length" field received in the Binding Cache that created or last modified this Binding Cache entry. This field is only valid if the "Prefix Scope Registration" flag or the "Home Registration" flag is set on this Binding Cache entry. If the "Prefix Scope Registration" flag is set, the "Prefix Length corresponds to the length of the mobile network prefix, otherwise the meaning is as defined in [4]. - if the "Prefix Scope Registration" flag is set, the "home address" corresponds to the mobile network prefix. 4.2.2. Searching the Binding Cache entries The Binding Cache is searched for an entry corresponding to the destination address of the packet. The destination address is compared with the home address field of entries recorded in the Binding Cache. If the "Prefix Scope Registration" flag is set in the entry under comparison, the comparison is made between the "Prefix Length" set of initial bits of the destination address and the "home address" field. If the prefix of the destination matches the mobile network prefix recorded in the entry, the destination is located in a mobile network. If the "Prefix Scope Registration" flag is not set, the comparison is made on the 128-bits addresses. If the Ernst and Bellier Expires 14 January 2001 [Page 10] INTERNET-DRAFT Mobile Networks Support in Mobile-IPv6 14 July 2000 destination address matches the home address, the destination is a mobile node. In both case, the care-of address of the corresponding entry is returned. 4.3. Enhanced Mobile IPv6 protocol operation The Mobile Node operation is enhanced to set the "P" to 1 and to fill the Mobile Network Prefix Sub-Option when it serves as the gateway of a mobile network. It is also enhanced to send Binding Updates to all CNs that communicate with one of its MNNs. The Correspondent Node and the Home Agent operations are enhanced to process the "P" bit recorded in the Binding Update option and to transmit via the care-of address of the mobile router all datagrams bearing a destination address matching the mobile network prefix. The following sections only describe changes according to sections 8, 9 and 10 of the Mobile IPv6 specification [4]. 4.3.1. Correspondent Node Operation Receiving Binding Updates Upon receiving a Binding Update, the CN performs validity checks as described in [4] section 8.2. If the Binding Update is valid, the CN creates a new entry in its Binding Cache for this mobile node as it is performed in [4]. In addition, if the "Prefix Scope Registration" bit in the Binding Update Option is set, the CN received a Binding Update from a Mobile Router serving a mobile network. In this case, the CN copies in the Binding Cache entry the "Prefix Scope Registration" bit from the Binding Update Option, the "Prefix Length" field from the Mobile Network Prefix Sub-Option, and the "Home Address" field from the Mobile Network Prefix" field in the Mobile Network Prefix Sub-Option. Sending Packets Before sending any packet, the sending node examine its Binding Cache for an entry for the destination address to which the packet is being sent (see section 4.2.2 "Searching the Binding Cache"). If the sending node has a Binding Ernst and Bellier Expires 14 January 2001 [Page 11] INTERNET-DRAFT Mobile Networks Support in Mobile-IPv6 14 July 2000 Cache entry, the sending node uses a routing header to route the packet to the destination node by way of the care-of address in the binding recorded in that Binding Cache entry. 4.3.2. Home Agent Operation Primary care-of address registration Upon receiving a Binding Update, the HA performs validity checks as described in [4] section 9.3. If the Binding Update is valid, the HA creates a new entry in its Binding Cache for this mobile node as it is performed in [4]. This entry is used for intercepting packets for the mobile node. In addition, if the "Prefix Scope Registration" bit in the Binding Update Option is set, the HA received a Binding Update from a Mobile Router serving a mobile network. In this case, the HA creates a second Binding Cache entry similar to the first one and copies the "Prefix Scope Registration" bit from the Binding Update Option, the "Prefix Length" field from the Mobile Network Prefix Sub- Option, and the "Home Address" field from the Mobile Network Prefix" field in the Mobile Network Prefix Sub-Option. This second entry is used for encapsulating packets destined to any node of the mobile network. Intercepting Packets Datagrams sent by the CN to the IP address of the MNN are routed towards the home link of the mobile router where they are intercepted by the HA as specified in [4] section 9.5. Tunneling Intercepted Packets to a Mobile Node For any packet sent to a mobile node or a MNN for which the Home Agent is the original sender of the packet, the Home Agent is operating as a correspondent node and the procedures described in section 4.3.2 apply. While acting as a Home Agent, the Home Agent intercepts any packet on the home link addressed to a mobile node or to a MNN. The Home Agent examines its Binding Cache for an entry for the destination address to which the packet is being sent (see section 4.2.2 "Searching the Binding Cache"). If the sending node has a Binding Cache entry, the Home Agent tunnels the packet to the care-of address recorded in that Binding Cache entry. Ernst and Bellier Expires 14 January 2001 [Page 12] INTERNET-DRAFT Mobile Networks Support in Mobile-IPv6 14 July 2000 4.3.3. Mobile Router Operation Sending Binding Updates Similarly to standard mobile nodes in the Mobile IPv6 specification [4], the Mobile Router obtains a new care-of address at each of its subsequent points of attachment using either stateless or stateful DHCPv6 address autoconfiguration. A Mobile Router serving as a gateway to a mobile network sends a Binding Update datagram to its Home Agent as specified in [4] section 10.6. In addition, it sets to "1" the Prefix Scope Registration" bit of the Binding Update Option and fills the "Prefix Length" and the "Mobile Network Prefix" fields of the Mobile Network Prefix Sub-Option. The Mobile Router learns the identity of its own CNs and CNs of its MNNs whenever it receives an encapsulated packet tunneled from its Home Agent. It therefore sends a Binding Update to the sender of the packet as described in [4] section 10.8 and fills its Binding List accordingly. In addition, it sets to "1" the Prefix Scope Registration" bit of the Binding Update Option and fills the "Prefix Length" and the "Mobile Network Prefix" fields of the Mobile Network Prefix Sub-Option. __________________________________________________ | | | CN | | Binding Cache: | | FECA:700:AAAA:103/56 -> FEC4:700:BBBB:202A:MR_ID | |__________________________________________________| | _________________|_________________ | | | | | Internet | | | |___________________________________| | | | FECA:700:BBBB:2020/64 | FECA:700:AAAA:1010/64 __|__ ____________________|_________________________________ | | | | | FG | | HA | | | | Binding Cache: | | | | FEC4:700:AAAA:103/56 -> FEC4:700:BBBB:202A:MR_ID | |_____| |______________________________________________________| Ernst and Bellier Expires 14 January 2001 [Page 13] INTERNET-DRAFT Mobile Networks Support in Mobile-IPv6 14 July 2000 | | | FEC4:700:BBBB:202A/64 FEC4:700:AAAA:1020 | _|_________________________________________ | | | | MR | | Home address FEC4:700:AAAA:1020:MR_ID | | Care-of address FEC4:700:BBBB:202A:MR_ID | |___________________________________________| | | __|__ __________|__________________ | | | | | MNN | | MNN-1 | | | | FECA:700:AAAA:103C:MNN-1_ID | |_____| |_____________________________| Figure 4 : Mobile Network Prefix is recorded in the Binding Cache 5. Security Issues There is no security concern although the care-of address is used for a set of destinations and not only for the particular destination that sent the Binding Update. Recipients of the prefix scope Binding Updates are not misled about the identity of its sender. The sender is clearly authenticated. We assume that the mobile router is somehow authenticated as a valid border router for the mobile network and is therefore allowed to send Binding Updates on behalf of the mobile network. 6. References [1] J. Bound and C. Perkins. Dynamic Host Configuration Protocol for IPv6 (DHCPv6), February 1999. Work in Progress [2] S. Thomson and T. Narten. IPv6 Stateless Address Autoconfiguration. RFC 2462, December 1998. [3] S. Deering and R. Hinden. Internet Protocol Version 6 (IPv6) Specification. RFC 2460, December 1998. [4] D. B. Johnson and C. Perkins. Mobility Support in IPv6, April 2000. Work in progress. [5] S. Kent and R. Atkinson. IP Authentication Header. RFC 2402, November 1998. [6] S. Kent and R. Atkinson. IP Encapsulating Security Payload (ESP). RFC 2406, November 1998. Ernst and Bellier Expires 14 January 2001 [Page 14] INTERNET-DRAFT Mobile Networks Support in Mobile-IPv6 14 July 2000 [7] J. D. Solomon. Mobile IP, The Internet Unplugged. Prentice Hall Series in Computer Networking and Distributed Systems. Prentice Hall PTR, 1998. ISBN 0-13-856246-6. [8] C. Perkins (Editor). IP Mobility Support. RFC 2002, October 1996. [9] C. E. Perkins. Mobile IP, Design Principles and Practices. Wireless Communications Series. Addison-Wesley, 1998. ISBN 0-201- 63469-4. [10] T. Narten, E. Nordmark, and W. Simpson. Neighbor Discovery for IP version 6 (IPv6). RFC 2461, December 1998. [11] C. Perkins and D. B. Johnson. Route Optimization in Mobile IP, Sun Microsystems and Carnegie Mellon University, February 2000. Work in progress. Author's Address Thierry Ernst INRIA PLANETE team ZIRST-655 avenue de l'Europe 38330 Montbonnot Saint Martin FRANCE Motorola Labs Espace Technologique - Saint Aubin 91193 Gif-sur-Yvette Cedex France Thierry.Ernst@inria.fr draft-ernst-mipv6-mobile-network-00.txt Ernst and Bellier Expires 14 January 2001 [Page 15]