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Versions: 00 01 02 03 04 05 06 rfc4886                                  
NEMO Working Group                                 Thierry Ernst, Editor
Internet-Draft                                            INRIA and WIDE
                                                          February, 2003

                "Network Mobility Support Requirements"

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

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   Network mobility arises when an entire network changes its point of
   attachment to the Internet and thus its reachability in the topology.
   The mobile network is viewed as a unit and is connected to the global
   Internet by one or more mobile routers. In contrast with host
   mobility support which aims at providing continuous Internet
   connectivity to mobile hosts only, network mobility support is to
   provide continuous Internet sessions not only to the mobile router
   connecting the mobile network to the global Internet, but also to
   nodes behind the mobile router. The purpose of this document is to
   list the requirements that must be met by network mobility support
   solutions in IPv6.

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Table of Contents

   1.   Introduction . . . . . . . . . . . . . . . . . . . . . . . . 03

   2.   Terminology. . . . . . . . . . . . . . . . . . . . . . . . . 04

   3.   Network Mobility Goals and Methodology . . . . . . . . . . . 04

   4.   General Purpose Guidelines for the Solutions . . . . . . . . 05

   5.   One-liner Requirements for Basic NEMO Support. . . . . . . . 09

   A.   Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . 11

   B.   References . . . . . . . . . . . . . . . . . . . . . . . . . 11

   C.   Editors' Addresses . . . . . . . . . . . . . . . . . . . . . 12

   D.   Full Copyright Statement . . . . . . . . . . . . . . . . . . 12

Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

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1. Introduction

   Network mobility support is concerned with managing the mobility of
   an entire network, viewed as a single unit, which changes its point
   of attachment to the Internet and thus its reachability in the
   Internet topology. Such kind of network is referred to as a mobile
   network and includes one or more mobile routers (MRs) which connect
   it to the global Internet. Nodes behind the MR(s) (MNNs) are both
   fixed (keeping the same address on the mobile network at all times),
   and mobile (entering and leaving the mobile network as they roam with
   respect to it). In most cases, the internal structure of the mobile
   network will in effect be relatively stable (no dynamic change of the
   topology), but this is not a general assumption.

   Cases of mobile networks include for instance:

      - networks attached to people (Personal Area Networks or PANs): a
      cell-phone with one cellular interface and one Bluetooth interface
      together with a Bluetooth-enabled PDA constitute a very simple
      instance of a mobile network.  The cell-phone is the mobile router
      while the PDA is used for web browsing or runs a personal web

      - networks of sensors and computers deployed in vehicles: vehicles
      are more and more embedded with a number of processing units for
      safety and ease of driving reasons, as advocated by ITS
      (Intelligent Transportation Systems) applications.

      - access networks deployed in public transportation (buses,
      trains, taxis, aircrafts): they provide Internet access to IP
      devices carried by passengers (laptop, camera, mobile phone: host
      mobility within network mobility or PANs: network mobility within
      network mobility, i.e. nested mobility).

      - ad-hoc networks connected to the Internet via a MR: for instance
      students in a train that both need to set up an ad-hoc network
      among themselves and to get Internet connectivity through the MR
      connecting the train to the Internet.

   Traditional work conducted so far on mobility support was to provide
   continuous Internet connectivity to mobile hosts only (host mobility
   support). In contrast with host mobility support, network mobility
   support is to provide continuous Internet sessions not only to the
   mobile router connecting the mobile network to the global Internet,
   but also to nodes behind the mobile router.

   Mobility of networks does not cause MNNs to change their own physical
   point of attachment, however they happen to change their topological

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   location with respect to the global Internet which results in lack of
   Internet access and broken sessions if no supporting mechanisms are
   deployed. In addition, communication between a MNN and an arbitrary
   Correspondent Node (CN) may result in extremely suboptimal paths,
   particularly when mobile networks are nested or when the CN is itself

   The mechanisms required for handling such mobility issues are
   currently lacking within the IETF standards. The NEMO working group
   has therefore been set up to deal with those. The purpose of this
   document is thus to detail the methodology that will be followed by
   the NEMO working group and to list requirements for network mobility

   This document is structured as follows: first, section 2 introduces
   the terminology for network mobility. In section 3, we define the
   goals and methodology of the working group and we emphasize the
   stepwise approach the working group has decided to follow. A number
   of guidelines are listed in section 4 and are used in section 5 to
   edict the requirements for basic network mobility support.

2. Terminology

   Terms used in this document are taken from [MIPv6] and [MOBILITY-
   TERMS]. Additional terms pertaining to network mobility specifically
   are defined in [NEMO-TERMS].

   [NOTE FROM THE EDITOR: parts from draft [NEMO-TERMS] will probably be
   moved to [MOBILITY-TERMS] whereas the remaining terms would then be
   pasted in this present document. THIS IS TO BE DISCUSSED]

3. Network Mobility Goals and Methodology

   The primary goal of the NEMO work is to specify a solution which
   allows mobile network nodes (MNNs) to remain connected to the
   Internet and continuously reachable at all times while the mobile
   network they are attached to changes its point of attachment.
   Secondary goals of the work is to investigate the effects of network
   mobility on various aspects of internet communication such as routing
   protocol changes, implications of realtime traffic and fast
   handovers, optimizations.  These should all support the primary goal
   of reachability for mobile network nodes. Security is an important
   consideration too, and efforts should be made to use existing
   solutions if they are appropriate.  Although a well-designed solution
   may include security inherent in other protocols, mobile networks
   also introduce new challenges.

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   For doing so, the NEMO working group has decided to take a stepwise
   approach by standardizing a basic solution to preserve session
   continuity (basic network mobility support), and at the same time
   study the possible approaches and issues with providing more optimal
   routing with potentially nested mobile networks (extended network
   mobility support). However, the working group is not chartered to
   actually standardize a solution to such route optimization at this
   point in time.

   For basic NEMO support, the working group will assume that none of
   the nodes behind the MR will be aware of the network's mobility, thus
   the network's movement needs to be completely transparent to the
   nodes inside the mobile network. This assumption will be made to
   accommodate nodes inside the network that are not generally aware of

   The efforts of the Mobile IP working group have resulted in the
   Mobile IPv4 [7] and Mobile IPv6 [6] protocols, which have already
   solved the issue of host mobility support. Since challenges to
   enabling mobile networks are vastly reduced by this work, basic
   network mobility support will adopt the methods for host mobility
   support used in Mobile IP, and extend them in the simplest way
   possible to achieve its goals. The basic support solution is for each
   MR to have a Home Agent, and use bidirectional tunneling between the
   MR and HA to preserve session continuity while the MR moves. The MR
   will acquire a Care-of-address from its attachment point much like
   what is done for mobile nodes (MN) using Mobile IP. This approach
   allows nested mobile networks, since each MR will appear to its
   attachment point as a single node.

4. General Purpose Guidelines for the Solutions

   This section lists a number of guidelines which are used to edict the
   requirements that MUST or SHOULD be met by forthcoming network
   mobility support solutions, for both basic NEMO support and extended
   NEMO support.

      - Migration Transparency: a permanent connectivity to the Internet
      MUST be provided to all MNNs while continuous sessions MUST be
      maintained as the mobile router changes its point of attachment.
      For doing so, MNNs will be reachable via their permanent IP

      - Performance Transparency (Seamless Mobility): NEMO support
      SHOULD provide limited signaling overhead and ideally SHOULD
      minimize the impact of handover on applications, in terms of
      packet loss or delay.  Variable delays of transmission and losses

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      between MNNs and their respective CNs as the network is moving are
      not considered lack of performance transparency.

      - Network Mobility Support Transparency: MNNs behind the MR(s)
      don't change their own point of attachment as a result of the
      mobile network's displacement in the Internet topology.
      Consequently, NEMO support is better performed by the sole MR(s)
      and specific support functions on any other nodes than the MR(s)
      SHOULD be avoided.

      - Operational Transparency: NEMO support MUST be implemented at
      the IP layer level. It MUST be transparent to any upper layer so
      that any upper layer protocol can run unchanged on top of an IP
      layer extended with NEMO support.

      - Arbitrary Configurations: The formation of a mobile network can
      exist in various levels of complexity. In the simplest case, a
      mobile network contains just a mobile router and a host.  In the
      most complicated case, a mobile network is multi-homed and is
      itself a multi-level aggregation of mobile networks with
      collectively thousands of mobile routers and hosts. While the list
      of potential configurations of mobile networks cannot be limited,
      at least the following configurations are desirable:

         o mobile networks of any size, ranging from a sole subnet with
           a few IP devices to a collection of subnets with a large
           number of IP devices,

         o multi-homed mobile network (see definition in [NEMO-TERMS].

         o foreign mobile nodes that attach to the mobile network.

         o nodes that change their point of attachment within the mobile

         o nested mobile networks (see definition in [NEMO-TERMS].

         o mobile networks displaced within a domain boundary (local
           mobility) or between domain boundaries (global mobility).

         o distinct mobility frequencies.

         o distinct access medium.

      In order to keep complexity minimal, transit networks are excluded
      from this list. A transit network is one in which data would be
      forwarded between two endpoints outside of the network, so that

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      the network itself simply serves as a transitional conduit for
      packet forwarding. A stub network (leaf network), on the other
      hand, does not serve as a data forwarding path. Data on a stub
      network is either sent by or addressed to a node located within
      that network.

      - Administration: the solution MUST not prevent mobile networks
      and mobile nodes owned by administratively different entities to
      attach to any part of the Internet topology for any other
      considerations than administrative and security policies (both
      global mobility and local-mobility are desirable).

      - Scalability: NEMO support signaling and processing MUST scale to
      a potentially large number of mobile networks irrespective of
      their configuration, mobility frequency, and number of CNs.

      - Backward Compatibility: NEMO support MUST be able to co-exist
      and not interfere with existing IPv6 standards. The solution MUST
      reuse standards defined in other IETF working groups and MAY only
      extend them if deemed necessary. For instance, the following
      mechanisms defined by other working groups MUST still function:

         o Address allocation and configuration mechanism.

         o Host mobility support: the solution MUST not prevent mobile
           nodes and correspondent nodes, either located within or
           outside the mobile network, to keep operating protocols
           defined by the Mobile IP working group.

         o Multicast support: the solution MUST maintain ongoing
           multicast sessions of MNNs as the mobile router changes its
           point of attachment. Group membership is currently gathered
           by MLD.

         o Access control protocols and mechanisms: NEMO support MUST
           not disallow protocols and mechanisms used by visiting mobile
           hosts and routers to be authenticated and authorized to gain
           access to the Internet via the mobile network infrastructure

         o Security protocols and mechanisms

         o Routing protocols and mechanisms: routers deployed in mobile
           networks may be routers like the others and therefrom are
           expected to run in some situations a number of protocols such
           as a routing protocol, Neighbor Discovery, ICMP, Router
           Renumbering and others. NEMO support MUST thus not prevent

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           usual routing protocols and mechanisms to keep working within
           the mobile network and to interact with the global Internet
           (home network only in the case of basic NEMO support) when

         o Seamless Mobility: the solutions MUST be compatible with

      - Security: NEMO support MUST comply with usual IETF security
      policies and recommendations and MUST have its specific security
      issues fully addressed. In practice, all NEMO support control
      messages transmitted in the network MUST ensure an acceptable
      level of security to prevent intruders to usurp identities.
      Specifically, the following issues have to be addressed:

         o Authentication of the sender to prevent identity usurpation.

         o Authorization, to make sure the sender is granted permission
           to perform the operation as indicated in the control message.

         o Confidentiality of the data contained in the control message.

         o Location Privacy: means to hide the actual location of MNNS
           to third parties other than the HA if desired.

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5. One-liner Requirements for Basic NEMO Support

   The NEMO WG will specify a unified and unique solution for "Basic
   Network Mobility Support". The solution will allow all nodes in the
   mobile network to be reachable via permanent IP addresses, as well as
   maintain ongoing sessions as the MR changes its point of attachment
   to the Internet topology. This will be done by maintaining a
   bidirectional tunnel between the MR and its Home Agent. The Working
   Group will investigate reusing the existing Mobile IPv6 mechanisms
   for the tunnel management, or extend it if deemed necessary.

   The following requirements are placed on the Basic NEMO support
   solution, hereafter referred to as "the solution":

   R01: The solution MUST be implemented at the IP layer level.

   R02: The solution MUST set up a bi-directional tunnel between
        MR and MR's Home Agent.

   R03: All traffic exchanged between a MNN and a CN in the global
        Internet MUST transit through the bidirectional tunnel.

   R04: MNNs MUST be reachable at a permanent IP address and name.

   R05: The solution MUST maintain continuous sessions (both unicast
        and multicast) between MNNs and arbitrary CNs after IP
        handover of (one of) the MR.

   R06: The solution MUST not require modifications to any node other
        than MRs and HAs.

   R07: The solution MUST support fixed nodes, mobile hosts and mobile
        routers in the mobile network.

   R08: The solution MUST allow MIPv6-enabled MNNs to use a mobile
        network link as either a home link or a foreign link.

   R09: The solution MUST not prevent the proper operation of Mobile
        IPv6 (i.e. the solution MUST support MIPv6-enabled MNNs and
        MUST also allow MNNs to receive and process Binding Updates
        from arbitrary Mobile Nodes.)

   R10: The solution MUST treat all the potential configurations the
        same way (whatever the number of subnets, MNNs, nested levels
        of MRs, egress interfaces, ...)

   R11: The solution MUST support mobile networks attaching to other
        mobile networks (nested mobile networks). Although it is not

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        fully clear how many layers of topology MUST be supported, or
        the complexity requirements of those nested networks, the goal
        is to support arbitrary levels of recursive networks, and only
        in the case where this is impractical and protocol concerns
        preclude this support should the solution impose restrictions on
        nesting (e.g. path MTU).

   R12: The solution MUST function for multi-homed mobile networks.
        More precisely:

        R13.1: The solution MUST support mobile networks with
               multiple MRs,

        R13.2: The solution MUST support MR with multiple interfaces,

        R13.3: The solution must support MR with multiple global
               addresses on an egress interface.

   R14: Signaling messages between the HA and the MR MUST be secured:

        R14.1: The receiver MUST be able to authenticate the sender

        R14.2: The function performed by the sender MUST be authorized
               for the content carried

        R14.3: Anti-replay MUST be provided

        R14.4: The signaling messages SHOULD be encrypted

   R15: The solution MUST ensure transparent continuation of routing and
        management operations over the bi-directional tunnel when the MR
        is away from home. (this includes e.g. routing protocols, router
        renumbering, DHCPv6, etc)

   R16: The solution MUST not impact on the routing fabric neither on
        the Internet addressing architecture

   R17: The solution MUST ensure backward compatibility with other
        standards defined by the IETF.

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A. Acknowledgments

   The material presented in this document takes most of its text from
   discussions and previous documents submitted to the NEMO working
   group. This includes initial contributions from Motorola, INRIA,
   Ericsson and Nokia. We are particularly grateful to Hesham Soliman
   (Ericsson) and the IETF ADs (Erik Nordmark and Thomas Narten) who
   highly helped to set up the NEMO working group. We are also grateful
   to all the following people whose comments highly contributed to the
   present document: TJ Kniveton (Nokia), Alexandru Petrescu (Motorola),
   Christophe Janneteau (Motorola), Pascal Thubert (CISCO), Hong-Yon
   Lach (Motorola), Mattias Petterson (Ericsson) and all the others
   people who have expressed their opinions on the NEMO (formely MONET)
   mailing list. Thierry Ernst wish to personally grant support to its
   previous employers, INRIA, and Motorola for their support and
   direction in bringing this topic up to the IETF, particularly Claude
   Castelluccia (INRIA) and Hong-Yon Lach (Motorola).

B. References

   [IPv6-NODE]      John Loughney
                    "IPv6 Node Requirements"
                    July 2002, Work in progress.

   [MIPv6]          David B. Johnson and C. Perkins.
                    "Mobility Support in IPv6"
                    January 2002. Work in progress.

                    "Mobility Related Terminology
                    August 2002. Work in progress

   [NEMO-TERMS]     Thierry Ernst and Hong-Yon Lach
                    "Terminology for Network Mobility Support",
                    Work in progress.

   [RFC1122]        R. Braden (editor).
                    "Requirements for Internet Hosts - Communication
                    Layers".  IETF RFC 1122, October 1989.

   [RFC2119]        S. Bradner
                    "Key words for use in RFCs to Indicate Requirement
                    Levels", BCP 14, RFC 2119, IETF, March 1997.

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   [RFC2460]        S. Deering and R. Hinden.
                    "Internet Protocol Version 6 (IPv6) Specification"
                    IETF RFC 2460, December 1998.

C. Editors's Addresses

   Questions about this document can be directed to the NEMO working
   group chairs:

      Thierry Ernst,
      Keio University.
      5322 Endo, Fujisawa-shi,
      Kanagawa 252-8520, Japan.
      Phone : +81-466-49-1100
      Fax   : +81-466-49-1395
      Email : ernst@sfc.wide.ad.jp

      T. J. Kniveton
      Communications Systems Lab
      Nokia Research Center
      313 Fairchild Drive
      Mountain View, California 94043, USA
      Phone : +1 650 625-2025
      Fax   : +1 650 625-2502
      EMail : Timothy.Kniveton@Nokia.com

D. Full Copyright Statement

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published and
   distributed, in whole or in part, without restriction of any kind,
   provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of developing
   Internet standards in which case the procedures for copyrights defined
   in the Internet Standards process must be followed, or as required to
   translate it into languages other than English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

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   This document and the information contained herein is provided on an

   Funding for the RFC editor function is currently provided by the
   Internet Society.

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