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Versions: (draft-ernst-monet-terminology) 00 01

IETF INTERNET-DRAFT                        Thierry Ernst, WIDE and INRIA
                                      Hong-Yon Lach, Motorola Labs Paris
                                                            October 2002

                  Network Mobility Support Terminology
                  draft-ernst-nemo-terminology-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 document proposes a terminology for defining network mobility
   problems and solution requirements. Network mobility occurs when an
   entire network changes its point of attachment to the Internet and
   thus its reachability in the topology, which is referred to as a
   mobile network.














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                                 Contents

Status of This Memo

Abstract

1. Introduction

2. Applications

3. Terminology
   3.1. Architecture Components
      Mobile Network
      Mobile Network Node (MNN)
      Mobile Router (MR)
      Fixed Node (FN)
      Mobile Node (MN)
      Node behind the MR
      Correspondent Node (CN)
      Access Router (AR)
      Egress Interface of a MR
      Ingress Interface of a MR
      Home subnet prefix
      Foreign subnet prefix
      Mobile Network Prefix
   3.2. Functional Terms
      Local Fixed Node (LFN)
      Local Mobile Node (LMN)
      Visiting Mobile Node (VMN)
      NEMO-enabled (NEMO-node)
      MIPv6-enabled (MIPv6-node)
   3.3. Nested Mobility
      root-NEMO
      parent-NEMO
      sub-NEMO
      Top-Level Mobile Router (TLMR)
   3.4. Multihomed mobile network
   3.5. Miscellaneous Terms
      NEMO support
      intra-domain mobility
      inter-domain mobility
      Idle MNN
      Idle Mobile Network

Acknowledgments

References




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 1. Introduction

   A mobile network is an entire network, moving as a unit, which
   changes its point of attachment to the Internet and thus its
   reachability in the topology. A mobile network may be composed by one
   or more IP-subnets and is connected to the global Internet via one or
   more Mobile Routers (MR). Nodes behind the MR primarily comprise
   fixed nodes (nodes unable to change their point of attachment while
   maintaining ongoing sessions), and additionally mobile nodes (nodes
   able to change their point of attachment while maintaining ongoing
   sessions). The internal configuration of the mobile network is
   assumed to be relatively stable with respect to the MR.

   If network mobility is not explicitly supported by some mechanisms
   once a MR changes its point of attachment, existing sessions between
   CNs and nodes behind the MR are broken, and connectivity to the
   global Internet is lost. In addition, fixed nodes behind the MR are
   faced with sub-optimal routing with their correspondents in the
   global Internet, whereas multiple levels of mobility may cause
   extremely sub-optimal routing.

   Traditional work on mobility support as conducted in the Mobile IP
   working group is to provide continuous Internet connectivity to
   mobile hosts only (host mobility support) and are unable to support
   network mobility. The NEMO working group has therefore been created
   to specify solutions specific for network mobility support.

   To describe the problems and to define the requirements that will
   have to be met by the solutions, a new terminology is needed, which
   is the object of the present document. This terminology is supposed
   to serve as the base document produced by the NEMO WG and shall be
   refined once we agree on the requirements.

  2. Applications

   Cases of mobile networks include networks attached to people
   (Personal Area Network or PAN, i.e. a network composed by all
   Internet appliances carried by people, like a PDA, a mobile phone, a
   digital camera, a laptop, etc.) and networks of sensors deployed in
   aircrafts, boats, busses, cars, trains, etc. An airline company that
   provides permanent on-board Internet access is an example of a mobile
   network. This allows passengers to use their laptops (this scenario
   is mentioned in [Tanenbaum] under section 1.2.4 and section 5.5.8;
   [Perkins] under section 5.12; [Solomon] under section 11.2; and
   [RFC2002] section 4.5), PDA, or mobile phone to connect to remote
   hosts, download music or video, browse the web. Passengers could
   themselves carry a network with them (a PAN). At the same time, air
   control traffic could be exchanged between the aircraft and air



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   traffic control stations (this scenario has already been investigated
   by Eurocontrol, the European Organization for the safety of air
   navigation. During a transatlantic flight, the aircraft changes its
   point of attachment to the Internet and may be reachable by distinct
   Internet Service Providers (ISPs). Over the oceans, the aircraft gets
   connected to the Internet through a geostationary satellite; over the
   ground, it's through a radio link. Handoffs do typically not occur
   very often (a radio link may cover 400-500 kilometers). Another
   similar scenario mentioning ships and aircrafts can be found in
   [RFC1726, section 5.15]. Similarly, a bus, the metropolitan public
   transport, or the taxi company could allow passengers to connect
   their PAN to the Internet via the embarked network, therefore
   ensuring, while on-board, an alternative to the metropolitan cellular
   network, in terms of price or available bandwidth, access control,
   etc. Meanwhile, a number of Internet appliances deployed in the
   mobile network are used to collect traffic and navigation data from
   the Internet while sensors within the mobile network collect and
   transmit to the Internet live information, like the current number of
   passengers, expected time to arrival, the amount of petrol left in
   the tank, etc. For a number of reasons (network management, security,
   performance,...), it is desirable to interconnect the Internet
   appliances deployed in cars, trains, busses by means of, for
   instance, an Ethernet cable, instead of connecting them individually
   and directly to the Internet, therefore exhibiting the need to
   displace an entire network.

 3. Terminology

   Terms introduced in this draft comply with the terminology already
   defined in the IPv6 [RFC2460] and Mobile IPv6 [MIPv6] specifications.
   Our terminology is primarily targeted toward IPv6 but is not
   necessarily limited to it. Some terms will only be useful for the
   purpose of defining the problem scope and functional requirements of
   network mobility support and shall be removed or refined once we
   agree on the requirements.

   The first section introduces terms to define the architecture
   components; the second introduces terms to discuss the requirements,
   the third, terms to discuss nested mobility; the forth defines
   multihoming, and the last, miscellaneous terms which do not fit in
   either sections.  The terminology summarized in fig.1 to 5. Fig.1
   shows a single mobile subnetwork. Fig.2. shows a larger mobile
   network comprising several subnetworks, attached on a foreign link.
   Fig.3 illustrates a node changing its point of attachment within the
   mobile network. Fig.4 and 5 illustrate nested mobility.

  3.1. Architecture Components




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   Mobile Network

      An entire network, moving as a unit, which dynamically changes its
      point of attachment to the Internet and thus its reachability in
      the topology. The mobile network is connected to the global
      Internet via one or more mobile router(s) (MRs). From the fixed
      Internet, the mobile network is a cloud. The internal
      configuration of the mobile network is assumed to be relatively
      stable with respect to the MR and is not a matter of concern. The
      internal of the mobile network will therefore not affect network
      mobility support protocols.

   Mobile Network Node (MNN)

      Any host or router located within the mobile network, either
      permanently or temporarily. A MNN could be any of a MR, LFN, VMN,
      or LMN. The distinction between LFN, LMN and VMN is necessary to
      discuss issues related to mobility management and access control,
      but does not preclude that mobility should be handled differently.
      Nodes are classified according to their function and capabilities.

            ____
           |    |
           | CN |
           |____|
          ___|____________________
         |                        |
         |                        |
         |       Internet         |
         |                        |
         |________________________|
            __|_            __|_
           |    |  Access  |    |
           | AR |  Router  | AR |
           |____|          |____|
        ______|__ foreign   __|_____________ home
                  link               __|_    link
                                    |    |
                                    | MR | Mobile Router
                                    |____|
                              _________|_______  internal
                               __|__     __|__   link
                              |     |   |     |
                              | MNN |   | MNN | Mobile Network Nodes
                              |_____|   |_____|

                      Figure 1: Architecture Components




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   Mobile Router (MR)

      A router which changes its point of attachment to the Internet.
      The MR has one or more egress interface(s) and one or more ingress
      interface(s) and acts as a gateway between the mobile network and
      the rest of the Internet. The MR thus maintains the Internet
      connectivity for the entire mobile network. When forwarding a
      packet to the Internet (i.e. upstream), the packet transmitted
      through one MR's egress interface; when forwarding a packet to the
      mobile network (i.e. downstream), the packet is transmitted
      through one of the MR's ingress interface.

   Fixed Node (FN)

      A node, either a host or a router, unable to change its point of
      attachment and its IP address without breaking open sessions. FNs
      are standard IPv6 nodes as defined in [IPv6-NODE] which do not
      support the MN functionality defined in [MIPv6] section 8.5 nor
      any other form of mobility support (also see [IPv6-NODE] section 7
      "Mobility").

   Mobile Node (MN)

      A node, either a host or a router, which is able to change its
      point of attachment and maintain continuous sessions.

   Node behind the MR

      Any MNN in a mobile network, beside the MRs connecting the mobile
      network to the Internet.

   Correspondent Node (CN)

      Any node that is communicating with one or more MNNs. A CN could
      itself be located within the mobile network.

   Access Router (AR)

      Any subsequent point of attachment of the MR at the network layer.
      Basically, a router on the home link or the foreign link. An AR
      may itself be located in a mobile network and provide access to
      mobile nodes.

   Egress Interface of a MR

      The interface attached to the home link if the MR is at home, or
      attached to a foreign link if the MR is in a foreign network.




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   Ingress Interface of a MR

      The interface attached to a link inside the mobile network. This
      interface is configured with the Mobile Network Prefix.

                  ________________________
                 |                        |
                 |                        |
                 |       Internet         |
                 |                        |
                 |________________________|
                         __|_
                Access  |    |
                Router  | AR |
                        |____|
             foreign _____|_____________
              link                   |
                                     | egress interface
                                   __|__
                             |    |    |
                    ingress  |____| MR | Mobile Router
                   interface |    |____|
                             |       |
                             |       | ingress interface
                             |   ____|________________ internal
                             |     __|__         __|__  link 1
                     _____   |    |     |       |     |
                    |     |__|    | LFN |       | LMN |
                    | LFN |  |    |_____|       |_____|
                    |_____|  |
                             | internal
                                link 2

                Figure 2: Larger Mobile Network with 2 subnets


   Home subnet prefix

      A bit string that consists of some number of initial bits of an IP
      address which identifies the MR's home link within the Internet
      topology (i.e. the IP subnet prefix corresponding to the mobile
      node's home address, as defined in [MIPv6]).

   Foreign subnet prefix

      A bit string that consists of some number of initial bits of an IP
      address which identifies the MR's foreign link within the Internet
      topology.



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   Mobile Network Prefix

      A bit string that consists of some number of initial bits of an IP
      address which identifies the entire mobile network within the
      Internet topology. All MNNs necessarily have an address named
      after this prefix.

  3.2. Functional Terms

   The distinction between LFN, LMN, and VMN as defined below it is a
   property of how different types of nodes can move in the topology.
   The rationale here is that nodes with different properties (may) have
   different requirements. This distinction may not be useful once we
   agree on the requirements. They are listed here as a means to ease
   and clarify the requirement discussion.

   Local Fixed Node (LFN)

      A fixed node (FN) that belongs to the mobile network and which
      doesn't move topologically with respect to the MR.

   Local Mobile Node (LMN)

      A mobile node (MN) or a mobile router (MR) that belongs to the
      mobile network (i.e. its home link is within the mobile network).
      It can move topologically with respect to the MR.

   Visiting Mobile Node (VMN)

      A mobile node (MN) or a mobile router (MR) that doesn't belong to
      the mobile network (i.e. its home link is not within the mobile
      network). A VMN that gets attached to a link within the mobile
      network obtains an address on that link and can move topologically
      with respect to the MR.

   NEMO-enabled (NEMO-node)

      A node that has been extended with network mobility support
      capabilities and that may take special actions based on that.
      (details of the capabilities are not known yet, but it may be
      implementing some sort of Route Optimization).

   MIPv6-enabled (MIPv6-node)

      A mobile node (MN) which is able to change its point of attachment
      and maintains continuous sessions thanks to the MN functionality
      as defined in [MIPv6] section 8.5.




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                  ________________________
                 |                        |
                 |                        |
                 |       Internet         |
                 |                        |
                 |________________________|
                    __|_            __|_
                   |    |  Access  |    |
                   | AR |  Router  | AR |
                   |____|          |____|
                    __|_         _____|_____________ foreign
                   |    |                     _|__   link
                   | MN |                 |  |    |
                   |____|         _____   |__| MR | Mobile Router
                                 |     |__|  |____|
                           |-->  | LMN |  |   __|_____________ internal
                           |     |_____|  |   __|__       |     link 1
                           |      _____   |  |     |
                           |     |     |__|  | LFN |
                           |     | LFN |  |  |_____|      |
                           |     |_____|  |               |
                           |              | internal      |
                           |                 link 2       |
                           |------------------------------|

                        Figure 3: LMN changing subnet




  3.3. Nested Mobility

   Nested mobility occurs when there are more than one level of
   mobility. A MNN acts as an Access Router and allows visiting nodes to
   get attached to it. There are two cases of nested mobility:

         - when the attaching node is a single node: VMN (see figure 4).
         For instance, when a passenger carrying a mobile phone gets
         Internet access from the public access network deployed into a
         bus.

         - when the attaching node is a router with nodes behind it,
         i.e.a mobile network (see figure 5). For instance, when a
         passenger carrying a PAN gets Internet access from the public
         access network deployed in the bus.






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                  ________________________
                 |                        |
                 |                        |
                 |       Internet         |
                 |                        |
                 |________________________|
                    __|_            __|_
                   |    |  Access  |    |
                   | AR |  Router  | AR |
                   |____|          |____|
                                _____|_____________ home
                     |                        _|__   link
                     |                    |  |    |
                     |            _____   |__| MR | Mobile Router
                     |           |     |__|  |____|
                     ----------> | VMN |  |   __|_____________ internal
                                 |_____|  |   __|__     __|__  link 1
                                  _____   |  |     |   |     |
                                 |     |__|  | LFN |   | LMN |
                                 | LFN |  |  |_____|   |_____|
                                 |_____|  |
                                          | internal link 2

      Figure 4: Nested Mobility: single VMN attached to a mobile network



      In the second case, a mobile network is getting attached to a
      larger mobile network and the aggregated hierarchy of mobile
      networks becomes a single nested mobile network. In this case, we
      use the following terms:

         - root-NEMO: the mobile network at the top of the nested
         hierarchy.

         - parent-NEMO: the upstream-NEMO providing access to a mobile
         network down the hierarchy

         - sub-NEMO: the downstream-NEMO attached to a mobile network up
         the hierarchy. It becomes a subservient of the parent-NEMO.

         - Top-Level Mobile Router (TLMR): the MR(s) of the root-NEMO
         which are used to connect the nested mobile network to the
         fixed Internet.







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                  ________________________
                 |                        |
                 |                        |
                 |       Internet         |
                 |                        |
                 |________________________|
                    __|_            __|_
                   |    |  Access  |    |
                   | AR |  Router  | AR |
                   |____|          |____|
                                _____|_____________ foreign
                                             _|__   link
                                         |  |    |
                               |  ____   |__| MR | Mobile Router (TLMR)
                               |_|    |__|  |____|
                               | | MR |  |   __|_____________ internal
                               | |____|  |   __|__     __|__  link 1
                       _____   |         |  |     |   |     |
                      |     |  |         |  | LFN |   | LMN |
                      | LFN |__|         |  |_____|   |_____|
                      |_____|  |         |
                               |         | internal
                                           link 2
                      <-----------------> <--------------------------->
                          sub-NEMO                 root-NEMO

      Figure 5: Nested Mobility: sub-NEMO attached to a larger mobile network



  3.4. Multihomed mobile network

   Multihoming, as currently defined by the IETF, covers site-
   multihoming [MULTI6] and host multihoming. Within host-multihoming, a
   host may be either:

      - multi-addressed: multiple source addresses to choose between on
      a given interface; all IPv6 nodes are multi-addressed due to the
      presence of link-local addresses on all interfaces.

      - multi-interfaced: multiple interfaces according to [RFC2460]
      definition.

      - multi-linked: just like multi-interfaced but all interfaces are
      NOT connected to the same link.

      - multi-sited: when using IPv6 site-local address and attached to
      different sites



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   So, a mobile network is multihomed when either:

      - a MR has multiple egress interfaces on the same foreign link

      - a MR has multiple egress interfaces on distinct foreign link

      - there are more than one MR in the mobile network


  3.5. Miscellaneous Terms

   Host mobility support

      Host Mobility Support allows mobile nodes to maintain session
      continuity. In IPv6, it is achieved by Mobile IPv6

   NEMO support

      Network mobility support allows mobile networks to maintain
      session continuity. Solutions developped to support NEtwork
      MObility will be referred to as "NEMO support".

      In Basic support, each Mobile Router has a Home Agent, and uses
      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 using Mobile IP. This approach allows nesting of
      Nemos, since each MR will appear to its attachment point as a
      single node.

      In Extended support, we will seek to optimize routing between MNNs
      and arbitrary CNs by some means which details are not known yet.

   intra-domain mobility

      Mobility within a single administrative domain, i.e. between
      subnetworks topologically close in the IP hierarchy. As an
      instance, the displacement of a node within a limited vicinity of
      adjacent subnetworks, like in a campus, that belong to the same
      organization or between ARs that belong to the same ISP. In the
      literature, and depending on the definition of ``closeness'', this
      is also termed intra-site mobility, local mobility or micro-
      mobility.

   inter-domain mobility

      Mobility across administrative domain boundaries, i.e. between
      subnetworks topologically distant in the IP hierarchy. As an



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      instance of Wide-Area Mobility, displacement of a node between
      distinct ISPs or organizations, or between widely separated sites
      of a single organization. In the literature, and depending on the
      definition of ``remoteness'', this is also termed inter-site
      mobility, global mobility, or macro-mobility.

   Idle MNN

      A MNN that does not engage in any communication.

   Idle Mobile Network

      A mobile network that does not engage in any communication outside
      the network may be considered idle from the global Internet. This
      doesn't preclude that MNNs are themselves idle. Internal traffic
      between any two MNNs located in the same mobile network is not
      concerned by this statement.


Acknowledgments

   The material presented in this document takes most of the text from
   our former internet-drafts submitted to MobileIP WG and to the former
   MONET BOF, which where themselves based on original text from
   [Ernst01]. Authors would therefore like to thank both Motorola Labs
   Paris and INRIA (PLANETE team, Grenoble, France), for the opportunity
   to bring this topic to the IETF since 2000, and particularly Claude
   Castelluccia (INRIA) for its advices, suggestions, and direction. We
   also acknowledge Alexandru Petrescu (Motorola), Christophe Janneteau
   (Motorola), Hesham Soliman (Ericsson) and Mattias Petterson
   (Ericsson) and all the people on the NEMO (formerly MONET) mailing
   list which helped to improve this draft.



















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References

   [Ernst01]   Thierry Ernst
               Network Mobility Support in IPv6", PhD Thesis,
               University Joseph Fourier Grenoble, France.
               October 2001. http://www.inria.fr/rrrt/tu-0714.html

   [MIPv6]     David B. Johnson and C. Perkins.
               "Mobility Support in IPv6".
               Internet Draft draft-ietf-mobileip-ipv6-18.txt,
               July 2002. Work in progress.

   [MULTI6]    B. Black, V. Gill and J. Abley
               "Requirements for IPv6 Site-Multihoming Architectures"
               draft-ietf-multi6-multihoming-requirements-03
               May 2002. Work in progress

   [IPv6-NODE] John Loughney
               "IPv6 Node Requirements"
               draft-ietf-ipv6-node-requirements-01.txt
               July 2002, Work in progress.

   [Perkins]   C. E. Perkins.
               "Mobile IP, Design Principles and Practices."
               Wireless Communications Series.
               Addison-Wesley, 1998. ISBN 0-201-63469-4.

   [RFC1726]   C. Partridge
               "Technical Criteria for Choosing IP the Next Generation",
               IETF RFC 1726 section 5.15, December 1994.

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

   [RFC2002]   C. Perkins (Editor).
               "IP Mobility Support".
               IETF RFC 2002,October 1996.

   [Solomon]   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.

   [Tanenbaum] Andrew Tanenbaum
               "Computer Networks",
               Prentice-Hall, Third Edition. 1996



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Author's Addresses

    Questions about this document can be directed to the authors:


      Thierry Ernst,
      INRIA, visiting researcher at WIDE
      Jun Murai lab. Faculty of Environmental Information,
      Keio University.
      5322 Endo, Fujisawa-shi, Kanagawa 252-8520, Japan.
      Phone : +81-466-49-1100
      Fax   : +81-466-49-1395
      E-mail: ernst@sfc.wide.ad.jp
      Web: http://www.sfc.wide.ad.jp/~ernst/

      Hong-Yon Lach
      Motorola Labs Paris, Lab Manager,
      Networking and Applications Lab (NAL)
      Espace Technologique - Saint Aubin
      91193 Gif-sur-Yvette Cedex, France
      Phone: +33-169-35-25-36
      Email: Hong-Yon.Lach@crm.mot.com





























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