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Versions: 00 01                                                         
MANET                                                         S. Ruffino
Internet-Draft                                                 P. Stupar
Expires: August 15, 2005                                           TILAB
                                                              T. Clausen
                                                                S. Singh
                                                             SAMSUNG AIT
                                                       February 11, 2005

                    Connectivity Scenarios for MANET

Status of this Memo

   This document is an Internet-Draft and is subject to all provisions
   of Section 3 of RFC 3667.  By submitting this Internet-Draft, each
   author represents that any applicable patent or other IPR claims of
   which he or she is aware have been or will be disclosed, and any of
   which he or she become aware will be disclosed, in accordance with
   RFC 3668.

   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 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

   The list of Internet-Draft Shadow Directories can be accessed at

   This Internet-Draft will expire on August 15, 2005.

Copyright Notice

   Copyright (C) The Internet Society (2005).


   This Internet Draft aims at describing a wide spread set of possible
   connectivity scenarios involving mobile ad-hoc networks, in order to

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   provide reference for standardization effort in this field.  The
   aspects considered for definition and classification of the scenarios
   are number and characteristics of the gateways that connect MANET
   nodes to external networks.  Analysis will range from a scenario
   where no connectivity is provided, i.e.  an isolated MANET, to more
   complex scenario where a MANET has multiple mobile Gateways.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Scenarios  . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     3.1   Isolated MANET . . . . . . . . . . . . . . . . . . . . . .  6
     3.2   MANET connected to an external network . . . . . . . . . .  6
       3.2.1   Fixed Gateways . . . . . . . . . . . . . . . . . . . .  8
       3.2.2   Mobile Gateways scenario . . . . . . . . . . . . . . .  9
     3.3   MANET intermittently connected to external networks  . . . 10
   4.  Roaming from a MANET to an Infrastructure Network  . . . . . . 11
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 15
   A.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 16
       Intellectual Property and Copyright Statements . . . . . . . . 17

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1.  Introduction

   MANET were initially designed to be employed in highly dynamic and
   unpredicatable environments, characterized by high mobility of users
   and terminals.  MANETs are essentially autonomous, self-configuring,
   self-healing networks, whose mobile nodes discover other nodes and
   supported services in an automatic fashion.  MANET routing protocols,
   as studied in IETF, enable two generic MANET nodes to exchange data
   traffic through multi-hop connections, if a 1-hop radio link between
   them is not available.  In this way, nodes can freely move within the
   MANET: routing protocols dynamically react to movement and constantly
   discover the optimal path according to a predifined metric, e.g.
   number of hops.  If an intermediary node, belonging to a path between
   a source and a destination, fails, traffic is automatically re-routed
   through an alternative path.

   RFC2501 [1] defines a MANET and also introduces the possibility to
   connect a MANET to an external network, by means of gateways.  These
   are devices equipped with two or more network interfaces: a MANET
   interface and an interface typically connected to one or more
   non-MANET networks.  MANET nodes exchange traffic among themselves
   using multi-hop paths and can reach outside hosts and the Internet by
   means of the gateways.  In this case the MANET acts as a "stub"
   network, whose nodes route traffic originating and/or terminating
   within the MANET itself.

   Operators, Network and Service providers show increasing interest in
   this type of network, as a consequence of the wide spread deployment
   of low-cost radio technologies such as IEEE802.11a/b/g/h and the
   increasing customer base.  Initially, commercial MANETs are expected
   to be deployed as an extension to the traditional infrastructure
   networks, to realize the so-called hybrid networks.

   An example of this networks are the Mesh Networks, used to extend the
   coverage area of a public hot-spot or to realize large-scale low-cost
   wireless coverage in urban areas.  A further interesting application
   and research field is represented by multi-hop cellular networks:
   MANETs connected to cellular WAN networks.  In this case MANETs can
   be used to realize an extended wireless coverage in areas where
   "traditional" cellular network is not available.

   Many proposals and projects that introduce integration between MANET
   and 3G+ networks exist: for example, see [2], [3], [4] and [5].

   This Internet Draft aims at describing and analyzing connectivity
   scenarios for MANET, to provide a reference for standardization
   effort in this field.  In fact, the scenarios described herein can be
   used as a starting point for the design of solutions to technical

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   problems, such as address autoconfiguration, gateway discovery,
   Duplicate Address Detection and global prefixes management.

   Analysis will range from a scenario where no connectivity is
   provided, i.e.  an isolated MANET, to more complex scenarios where a
   MANET has multiple mobile Gateways.  This document is structured in
   the following way: in Section 2 a glossary for commonly used terms is
   given; in Section 3 connectivity scenarios for a MANET are listed.
   In this section particular attention is paid to the connection of a
   MANET with other external networks, by means of one or more fixed
   (Section 3.2.1) or mobile wireless gateways (Section 3.2.2).  In
   Section 4 the roaming of a node from a Infrastractured wireless LAN
   to an ad-hoc network is considered.

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2.  Terminology

      An IPv4/IPv6 device which is a MANET element: it runs a MANET
      routing protocol and exchanges data with other nodes within a
      MANET and with hosts located within external networks.  A node has
      at least one physical interface connecting it to the MANET.

      A node equipped with at least two interfaces, one of which
      connects it to an external network, i.e.  non-MANET, and can be
      wired or wireless.

      An IPv4/IPv6 terminal/computer, external to the MANET.  Host is
      defined here as only "External" to differentiate it from the nodes
      of the MANET.

   Wireless Interface (or MANET interface)
      The physical network interface that connects a node to the MANET.

   Radio Interface (or Cellular Interface)
      The physical network interface that can connect a gateway to an
      external Wireless Wide Area Network, owned and administered by an

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3.  Scenarios

   In this section, we describe the typical connectivity scenarios of a
   MANET.  This section is structured as follows: first, the case of an
   isolated MANET is examined, where no gateways exist.  Then, various
   scenarios of a connected MANET are given, classified by the
   characteristics and the number of gateways, which can be fixed and/or
   mobile.  In the end, the case of an intermittently connected MANET is

3.1  Isolated MANET

   An isolated MANET is a network that is autonomously set-up among
   wireless mobile nodes localized in the same geographical area.  Nodes
   activate Layer 2 radio links, by which they can exchange traffic with
   their neighbors, and run an ad-hoc routing protocol, which enables
   multi-hop data forwarding through intermediate nodes.  Routing
   protocol constantly discovers routes between nodes, in a proactive
   ([13], [15]) or reactive fashion ([14], [16]): this enables each node
   to route traffic to all other nodes within the MANET also during

   In this type of MANET there is no connection to an external network:
   all traffic is generated by MANET nodes and addressed to MANET nodes.

   Typical applications of this scenario are temporary networks, that
   must be set-up in areas where neither wireless coverage nor
   infrastructure exist.  Examples can be emergency networks used for
   disaster recovery, battlefield applications, electronic surveillance.
   Other examples can be found in occasional work meetings, where
   networks are set-up to enable file sharing among co-workers.

3.2  MANET connected to an external network

   In this scenario a MANET is connected to an external network by means
   of one or more gateways (Figure 1).  A generic MANET node can
   exchange data traffic with every other node through multi-hop paths
   and communicate with hosts located in the external network, routing
   its uplink traffic towards a gateway.  Such gateway, in turn, will
   receive return traffic from the host and will route it to the source

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                               |   Internet    |**
                               +---------------+  *
                                 *           *     *
                                 *           *      *
                             GW1**           *       GW3
                               |         +--GW2-------+
                               |         |   |
                            ---N1--------+   |
                           /      \          |
                         N4        \        N2

         Figure 1: MANET interconnected to an external network

   Gateways play a critical role here.  If the number of nodes in the
   MANET increases, gateways can become bottlenecks, as they route an
   increasing and possibily huge amount of traffic.  This also depends
   on the available bandwidth on the uplink interface.  Moreover,
   gateways can be equipped with a number of additional features.  For
   example, they could participate to the external routing protocol, in
   order to announce internal routes to external routers and hosts,
   possibly performing some kind of aggregation.  They can act as
   enforcement points for security purposes: they can control access to
   external networks and, following a common practice, they can enforce
   Ingress Filtering on MANET generated traffic.  Finally they can also
   provide services like DNS to MANET nodes.

   This scenario can be expanded, depending on the characteristics of
   the network interface connecting gateways to the external network: it
   can be either wired or wireless, which can, in turn, be of a
   different type with respect to the MANET interface.  In the first
   case Gateways are fixed, while in the second case they can also be
   mobile, as the other MANET nodes.

   Moreover, a MANET can have only one gateway (fixed or mobile) or can
   have multiple gateways (fixed or mobile).  Other than guaranteeing a
   high degree of reliability and fault tolerance to the entire MANET,
   the presence of multiple gateways enables load balancing among the
   gateways themselves.  This can be very useful especially when the
   external network is a low-throughput cellular WAN, such as GPRS/EDGE,
   in order not to overload a single gateway with traffic potentially
   generated by many nodes at the same time.  Single traffic flows of
   multiple nodes or many flows of a single node can be routed through

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   different gateways, consequently implying an improvement of the
   overall performances of the MANET.

   Gateways can also be equipped with additional resources in order to
   grant better fault tolerance to the entire MANET: additional energy
   resources, more processing power, more volatile and non-volatile
   memory.  This is especially true in case of fixed gateways, that can
   be directly powered and directly operated.

   The following sections detail usage scenarios for fixed and mobile

3.2.1  Fixed Gateways

   In this scenario, gateways are deployed in predefined positions
   planned by the network operator.  Each gateway is connected to the
   external network by means of a wired or wireless interface.

   Mesh networks and networks used for environmental surveillance can be
   categorized under this scenario.

   o  Mesh Networks: these are probably the most widespread ad-hoc
      networks.  In a Mesh Network, user terminals (nodes) exchange
      traffic between them directly through a layer-2 radio link and
      using other nodes or fixed wireless devices as intermediate
      relays.  A Mesh Network is typically connected to an external
      infrastructure network by means of fixed wired Access Points,
      which act as gateways and typically connect the Mesh to an
      external infrastructure network.
      Mesh Networks can be further classified depending on the kind of
      devices which form the mesh itself.  In fact, in some deployments,
      the mesh is realized only among the wireless Access Points, which
      are devices endowed with two wireless interfaces: the first
      interface forms the mesh with other peer access points,
      participating to a routing protocol, the second interface provides
      local connectivity to nodes, which cannot set-up a network
      themselves, as they don't run any routing protocol.  In another
      case the mesh is realized among all the nodes, which have to run a
      routing protocol.
      Applications of this networks are Internet public access
      (browsing, email etc.) by mobile users from outdoor areas,
      wireless coverage of corporate building to give employees access
      to shared data and commonly used services (email, Intranet
      browswing).  These solutions can bring to savings on cabling and
      maintenance costs.

   o  Surveillance networks: several wireless nodes endowed with sensors
      of various kinds are spread over high enviromental risk areas

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      (e.g.  fires in wooden areas).  They communicate through multi-hop
      connections and run a routing protocol.  When an emergency
      situation arises, data collected by sensors are transmitted from
      the collecting nodes upwards one or more gateways (which can have
      both a wired or wireless interface) and conveyed to a manned
      monitoring station.
      Topologies of this kind of network are typically static, as the
      nodes are installed in fixed positions within the monitored areas.
      Moreover, these networks are characterized by multiple constant
      low-throughput data flows going from the sensors to the gateways.

3.2.2  Mobile Gateways scenario

   In this scenario, the gateway's radio interface, connecting the MANET
   to the external network, can be a cellular WAN interface (GSM, GPRS,
   EDGE, UMTS), a broadband wireless MAN (WMAN) interface (e.g.
   802.16x, 802.20) or a WLAN interface (802.11a/b/g/h/j).  In each of
   these cases, gateways can forward uplink traffic outside the MANET
   only if located within the transmission/reception range of one or
   more Base Stations or Access points.  Gateways not only can move
   freely within the coverage area, but they can also move outside this
   area.  In such case, the gateway can't forward uplink traffic
   destined to external hosts anymore, nor downlink traffic destined to
   internal nodes.

   In this outlined scenario, the MANET can be seen as a coverage
   extension of the radio infrastractured network to which the gateways
   are connected.  The primary benefit of such extension is that local
   communication between two nodes is performed without using any
   cellular radio resource, e.g.  radio channels.  Another benefit is
   the possibility to grant network access also to those terminals that
   are not equipped with a cellular radio interface (e.g.  access
   sharing).  The implication of this business model on security,
   accounting and rewarding aspects are out of the scope of this draft,
   neverthless must be carefully investigated.

   A more advanced scenario can be realized when most of the nodes are
   also equipped with two heterogeneous interfaces.  In this case
   gateways can be "occasional": they can be nodes that, after setting
   up the connection towards the external network, whenever located
   within its coverage area, can start forwarding other nodes' outbound
   packets.  In this kind of scenario, gateways can be "special" nodes
   endowed with additional features, but they can also be ordinary MANET
   nodes, such as mobile phones and PDAs.  In this last case, gateways
   are characterized by low computational power and limited energy
   resources.  Although the MANET can again exploit benefits given by
   multiple gateways, additional issues arise: in fact, gateways are not
   under operators control anymore.  It's possible that the owner of the

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   gateway establishes abruplty to turn his terminal off or to tear down
   the connection towards the cellular network, in order to save battery
   life.  Thus, the number and the position of gateways are higly
   dynamic and this can cause frequent re-routing of uplink data flows.

   o  Automotive scenario: a MANET is set up by a group of vehicles.
      One or more of these may become a mobile gateway after connecting
      to the Wireless LAN of a petrol station or setting up an UMTS
      connection and, therefore, may be used by the other vehicles of
      the MANET to exchange traffic with the external hosts.

3.3  MANET intermittently connected to external networks

   Gateways in a MANET, especially if mobile and equipped with a radio
   interface, may not be permanently connected to the external network.
   MANETs of this kind have the characteristics of both MANET described
   in Section 3.1 (while not connected) and of the ones described in
   Section 3.2 (while connected).

   Most of the nodes belonging to a MANET of this kind shall exploit the
   connection temporally set up to an external network to communicate
   with hosts they can't reach while the MANET is isolated.  As a
   consequence, such MANETs may experience a burst of exchanged traffic
   while connected to the external network.  The amount and the
   distribution of such traffic depends on how long the MANET can be
   connected to an external network.

   o  Train network: a MANET built in a train, which is connected while
      stopped at the station and disconnected otherwise.  In particular,
      if the MANET is set up by some passengers, it may happen that
      while the train is stopped at the station, some of the nodes may
      become gateways.  For example, the station area may be covered by
      a wireless technology and some nodes equipped with a non-MANET
      interface of the same technology may therefore set up a connection
      to the external network.  In this case, most of the users may use
      the gateways to connect to their mail server, download and
      eventually send their e-mails: the MANET they belong to may
      therefore experience a burst of traffic exchanged with the
      external network.

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4.  Roaming from a MANET to an Infrastructure Network

   A mobile node, connected e.g.  to a IEEE 802.11 network
   (infrastructure mode), can roam to a nearby IEEE 802.11 (ad-hoc mode)
   MANET.  This situation can be very commonly experienced by a mobile
   node, during its movement, even not voluntarily.  It is worth noting
   that such roaming doesn't involve only layer-2 operations.  It is
   indeed likely that the procedures used within IEEE 802.11 network,
   e.g.  for address configuration or duplicate address detection, are
   different from those used in a MANET.  This is mainly due to the fact
   that a MANET is characterized by multi-hop paths while in a WLAN all
   hosts are connected to the same link.

   There can be also situation where the destination MANET uses a
   different radio technology for multi-hop links.  This scenario, not
   addressed in this document, brings added difficulties, because radio
   interface should be dynamically switched to use a different Layer 1
   and 2 technology.

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5.  Security Considerations

   This document raises no security issue.

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6.  IANA Considerations

   This document has no actions for IANA.

7.  References

   [1]   Corson, S. and J. Macker, "Mobile ad hoc networking (MANET):
         Routing protocol performance issues and evaluation
         considerations", RFC 2501, January 1999.

   [2]   Siebert, M., "On Ad Hoc Networks in the 4G Integration
         Process", Med-Hoc 2004 , June 2004.

   [3]   "Ambient Networks", http://www.ambient-networks.org .

   [4]   "Daidalos", http://www.ist-daidalos.org .

   [5]   "World Wireless Research Forum",
         http://www.wireless-world-research.org .

   [6]   Wakikawa, R., Malinen, J., Perkins, C., Nilsson, A. and A.
         Tuominen, "Global connectivity for IPv6 Mobile Ad Hoc
         Networks", I-D draft-wakikawa-manet-globalv6-03.txt, October

   [7]   Cha, H., Park, J. and H. Kim, "Extended Support for Global
         Connectivity for IPv6 Mobile Ad Hoc Networks", October 2003.

   [8]   Jeong, J., Park, J., Kim, H. and D. Kim, "Ad Hoc IP Address
         I-D draft-jeong-adhoc-ip-addr-autoconf-02.txt, February 2004.

   [9]   Perkins, C., Malinen, J., Wakikawa, R. and E. Belding-Royer,
         "IP Address Autoconfiguration for Ad Hoc Networks",
         I-D draft-perkins-manet-autoconf-01.txt, November 2001.

   [10]  Singh, S., Kim, JH., Choi, YG., Kang, KL. and YS. Roh, "Mobile
         multi-gateway support for IPv6 mobile ad hoc networks",
         I-D draft-singh-manet-mmg-00.txt, June 2004.

   [11]  Paakkonen, P., Rantonen, M. and J. Latvakoski, "IPv6 addressing
         in a heterogeneous MANET-network",
         I-D draft-paakkonen-addressing-htr-manet-00.txt, December 2003.

   [12]  Jelger, C., Noel, T. and A. Frey, "Gateway and address
         autoconfiguration for IPv6 adhoc networks",
         I-D draft-jelger-manet-gateway-autoconf-v6-02.txt, April 2004.

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   [13]  Clausen, T. and P. Jacquet, "Optimized link state routing
         protocol", RFC 3626, October 2003.

   [14]  Perkins, C., Belding-Royer, E. and S. Das, "Ad hoc On-Demand
         Distance Vector (AODV) Routing", RFC 3561, July 2003.

   [15]  Ogier, R., Templin, F. and M. Lewis, "Topology Dissemination
         Based on Reverse-Path Forwarding (TBRPF)", RFC 3684, February

   [16]  Johnson, D., Maltz, D. and Y. Hu, "The Dynamic Source Routing
         Protocol for Mobile Ad Hoc Networks (DSR)",
         I-D draft-ietf-manet-dsr-10.txt, July 2004.

   [17]  Postel, J., "Internet Protocol", STD 5, RFC 791, September

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

   [19]  Thomson, S. and T. Narten, "IPv6 Stateless Address
         Autoconfiguration", RFC 2462, December 1998.

   [20]  Aboba, B., "Dynamic Configuration of Link-Local IPv4
         Internet-Draft draft-ietf-zeroconf-ipv4-linklocal-17, July

   [21]  Johnson, D., Perkins, C. and J. Arkko, "Mobility Support in
         IPv6", RFC 3775, June 2004.

   [22]  Sun, Y. and E. Belding-Royer, "A study of dynamic addressing
         techniques in mobile ad hod networks", I-D Wireless
         communication and mobile computing, May 2004.

   [23]  Narten, T., Nordmark, E. and W. Simpson, "Neighbor Discovery
         for IP Version 6 (IPv6)", RFC 2461, December 1998.

   [24]  Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic Host
         Configuration Protocol (DHCP) version 6", RFC 3633, December

   [25]  Engelstad, P., T°nnesen, A., Hafslund, A. and G. Egeland,
         "Internet Connectivity for Multi-Homed Proactive Ad Hoc
         Networks", First IEEE International Conference on Sensor and Ad
         hoc Communications and Networks , October 2004.

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Authors' Addresses

   Simone Ruffino
   Telecom Italia LAB
   Via G.Reiss Romoli 274
   Torino  10148

   Phone: +39 011 228 7566
   Email: simone.ruffino@telecomitalia.it

   Patrick Stupar
   Telecom Italia LAB
   Via G.Reiss Romoli 274
   Torino  10148

   Phone: +39 011 228 5727
   Email: patrick.stupar@telecomitalia.it

   Thomas Heide Clausen
   Laboratoire d'informatique
   Ecole Polytechnique
   Palaiseau Cedex  91128

   Phone: +33 1 6933 2867
   Email: thomas.clausen@polytechnique.fr

   Shubhranshu Singh
   SAMSUNG Advanced Institute of Technology - i-Networking Laboratory
   San 14-1, Nongseo-ri, Giheung-eup
   Yongin-si,  Gyeonggi-do 449-712

   Phone: +82 31 280 9569
   Email: shubhranshu@samsung.com

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Appendix A.  Acknowledgments

  The authors would like to thank Ivano Guardini for his valuable

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