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Network Working Group                                         J. SolomonRequest for Comments: 2005                                      MotorolaCategory: Standards Track                                   October 1996Applicability Statement for IP Mobility SupportStatus of this Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   Official Protocol Standards" (STD 1) for the standardization state   and status of this protocol.  Distribution of this memo is unlimited.Abstract   As required by [RFC 1264], this report discusses the applicability of   Mobile IP to provide host mobility in the Internet.  In particular,   this document describes the key features of Mobile IP and shows how   the requirements for advancement to Proposed Standard RFC have been   satisfied.1. Protocol Overview   Mobile IP provides an efficient, scalable mechanism for node mobility   within the Internet.  Using Mobile IP, nodes may change their point-   of-attachment to the Internet without changing their IP address.   This allows them to maintain transport and higher-layer connections   while moving.  Node mobility is realized without the need to   propagate host-specific routes throughout the Internet routing   fabric.  The protocol is documented in [MIP-PROTO].   In brief, Mobile IP routing works as follows.  Packets destined to a   mobile node are routed first to its home network -- a network   identified by the network prefix of the mobile node's (permanent)   home address.  At the home network, the mobile node's home agent   intercepts such packets and tunnels them to the mobile node's most   recently reported care-of address.  At the endpoint of the tunnel,   the inner packets are decapsulated and delivered to the mobile node.   In the reverse direction, packets sourced by mobile nodes are routed   to their destination using standard IP routing mechanisms.   Thus, Mobile IP relies on protocol tunneling to deliver packets to   mobile nodes that are away from their home network.  The mobile   node's home address is hidden from routers along the path from the   home agent to the mobile node due to the presence of the tunnel.  The   encapsulating packet is destined to the mobile node's care-of addressSolomon                     Standards Track                     [Page 1]

RFC 2005           Mobile IP Applicability Statement        October 1996   -- a topologically significant address -- to which standard IP   routing mechanisms can deliver packets.   The Mobile IP protocol defines the following:   - an authenticated registration procedure by which a mobile node     informs its home agent(s) of its care-of address(es);   - an extension to ICMP Router Discovery [RFC1256] which allows mobile     nodes to discover prospective home agents and foreign agents; and   - the rules for routing packets to and from mobile nodes, including     the specification of one mandatory tunneling mechanism ([MIP-IPinIP])     and several optional tunneling mechanisms ([MIP-MINENC] and     [RFC1701]).2. Applicability   Mobile IP is intended to solve node mobility across changes in IP   subnet.  It is just as suitable for mobility across homogeneous media   as it is for mobility across heterogeneous media.  That is, Mobile IP   facilitates node movement from one Ethernet segment to another as   well as it accommodates node movement from an Ethernet segment to a   wireless LAN.   One can think of Mobile IP as solving the "macro" mobility management   problem.  It is less well suited for more "micro" mobility management   applications -- for example, handoff amongst wireless transceivers,   each of which covers only a very small geographic area.  In this   later situation, link-layer mechanisms for link maintenance (i.e.   link-layer handoff) might offer faster convergence and less overhead   than Mobile IP.   Mobile IP scales to handle a large number of mobile nodes in the   Internet.  Without route optimization as described in [MIP-OPTIM],   however, the home agent is a potential load point when serving many   mobile nodes.  When home agents become overburdened, additional home   agents can be added -- and even dynamically discovered by mobile   nodes -- using mechanisms defined in the Mobile IP documents.   Finally, it is noted that mobile nodes are assigned (home) IP   addresses largely the same way in which stationary hosts are assigned   long-term IP addresses; namely, by the authority who owns them.   Properly applied, Mobile IP allows mobile nodes to communicate using   only their home address regardless of their current location.  Mobile   IP, therefore, makes no attempt to solve the problems related to   local or global, IP address, renumbering.Solomon                     Standards Track                     [Page 2]

RFC 2005           Mobile IP Applicability Statement        October 19963. Security   Mobile IP mandates the use of cryptographically strong authentication   for all registration messages exchanged between a mobile node and its   home agent.  Optionally, strong authentication can be used between   foreign agents and mobile nodes or home agents.  Replay protection is   realized via one of two possible mechanisms -- timestamps or nonces.   Due to the unavailability of an Internet key management protocol,   agent discovery messages are not required to be authenticated.   All Mobile IP implementations are required to support, at a minimum,   keyed MD5 authentication with manual key distribution.  Other   authentication and key distribution algorithms may be supported.   Mobile IP defines security mechanisms only for the registration   protocol.  Implementations requiring privacy and/or authentication of   data packets sent to and from a mobile node should use the IP   security protocols described in RFCs 1827 and 1826 for this purpose.4. MIB   At the time of publication of this Applicability Statement, a   Management Information Base (MIB) for Mobile IP has been written and   documented inRFC 2006.5. Implementations   Several implementations of Mobile IP are known to exist.  The   following list gives the origin and a contact for several such   implementations:      Organization:   Contact:      CMU             Dave Johnson <dbj@cs.cmu.edu>      FTP Software    Frank Kastenholz <kasten@ftp.com>      IBM             Charlie Perkins <perk@watson.ibm.com>      Motorola        Jim Solomon <solomon@comm.mot.com>      Nokia           Gunyho Gabor <gunyho@ncsmsg07he.ntc.nokia.com>      SUN             Gabriel Montenegro <gab@cali.Eng.Sun.COM>      Telxon          Frank Ciotti <frankc@teleng.eng.telxon.com>6. Implementation Experience   FTP Software hosted an interim meeting, October 23-27, 1995 in which   interoperability of several implementations was demonstrated.  The   following major features of the Mobile IP protocol were tested:Solomon                     Standards Track                     [Page 3]

RFC 2005           Mobile IP Applicability Statement        October 1996   1)  Mobile Nodes receiving and processing Agent Advertisements.   2)  Agents receiving Agent Solicitations and responding with Agent       Advertisements.   3)  Mobile Nodes registering with foreign agents on foreign networks.   4)  Packets being received by the mobile node after having been       tunneled by the home agent and de-tunneled by the foreign agent.   5)  Packets from the mobile node being routed directly to their       destinations.   6)  Mobile nodes discovering that their connectivity/subnet had       changed and re-registering at their new location.   7)  Mobile nodes discovering that their current foreign agent had       rebooted and therefore re-registering with that foreign agent.   8)  The required form of tunneling (IP-in-IP encapsulation       [MIP-IPinIP]) as well as the one of the optional forms of tunneling;       namely, Minimal Encapsulation [MIP-MINENC].   9)  Mobile nodes de-registering upon returning to their home network.   10) Registrations being rejected for authentication failures,       including invalid authenticators as well as mismatched       identification values (replay protection).   11) TCP connections remaining open (with data flowing) while a mobile       node moved from its home network to a foreign network and then       back again to the home network.   Interoperability of at least two independent implementations was   demonstrated for all of the features listed above.7. Summary   The co-chairs, on behalf of the working group participants, believe   that the Mobile IP working group has satisfied the requirements set   forth in [RFC1264] for the advancement of Mobile IP to Proposed   Standard RFC.  Specifically, the technical specification document is   stable, a MIB has been written, the security architecture has been   set forth in accordance with IAB principles, and several independent   implementations have been demonstrated to be interoperable.8. References   [RFC1256] Deering, S., Editor, "ICMP Router Discovery Messages",RFC1256, September 1991.   [RFC1701] Hanks, S. et. al., "Generic Routing Encapsulation (GRE)",RFC 1701, October 1994.   [RFC1264] Hinden, R., "Internet Routing Protocol Standardization      Criteria",RFC 1264, October 1991.Solomon                     Standards Track                     [Page 4]

RFC 2005           Mobile IP Applicability Statement        October 1996   [MIP-IPinIP] Perkins, C., Editor, "IP Encapsulation within IP",RFC 2003, October 1996.   [MIP-OPTIM] Johnson, D., and C. Perkins, "Route Optimization in      Mobile IP", Work in Progress.   [MIP-PROTO] Perkins, C., Editor, "IP Mobility Support",RFC 2002,      October 1996.   [MIP-MINENC] Perkins, C., Editor, "Minimal Encapsulation within IP",RFC 2004, October 1994.9. Author's Address   Questions about this memo can be directed to:   Jim Solomon   Motorola Inc.   1301 E. Algonquin Rd. - Rm 2240   Schaumburg, IL  60196   Voice:  +1-847-576-2753   Fax:    +1-847-576-3240   EMail: solomon@comm.mot.comSolomon                     Standards Track                     [Page 5]