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MANET Autoconfiguration (AUTOCONF)                          C. Bernardos
Internet-Draft                                               M. Calderon
Intended status: Informational                                      UC3M
Expires: May 6, 2009                                         H. Moustafa
                                                          France Telecom
                                                        November 2, 2008


      Survey of IP address autoconfiguration mechanisms for MANETs
                draft-bernardos-manet-autoconf-survey-04

Status of this Memo

   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 becomes
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   This Internet-Draft will expire on May 6, 2009.
















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Abstract

   This Internet Draft provides a detailed description of most of the
   existing IP autoconfiguration solutions proposed so far.  The main
   aim of this document is to serve as a general reference for the
   AUTOCONF solution space.  We present most of the previously proposed
   IP AUTOCONF mechanisms in MANETs, showing their key characteristics,
   conforming to the AUTOCONF problem statement draft and the MANET
   architecture draft.  Furthermore, each solution is analysed based on
   a number of evaluation considerations.









































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Table of Contents

   1.  Introduction and motivation  . . . . . . . . . . . . . . . . .  5
   2.  IP address auto-configuration protocols  . . . . . . . . . . .  7
     2.1.  Solutions for Standalone MANET scenarios . . . . . . . . .  7
       2.1.1.  No merging support . . . . . . . . . . . . . . . . . .  7
         2.1.1.1.  IP address Autoconfiguration for Ad Hoc
                   Networks (Perkins et al.)  . . . . . . . . . . . .  7
       2.1.2.  Merging support  . . . . . . . . . . . . . . . . . . .  9
         2.1.2.1.  IPv6 Autoconfiguration in Large Scale Mobile
                   Ad-Hoc Networks (Weniger et al.) . . . . . . . . .  9
         2.1.2.2.  Ad Hoc IP Address Autoconfiguration (Jeong et
                   al.) . . . . . . . . . . . . . . . . . . . . . . . 10
         2.1.2.3.  IP Address Assignment in a Mobile Ad Hoc
                   Network (Mohsin et al.)  . . . . . . . . . . . . . 12
         2.1.2.4.  An Address Assignment for the Automatic
                   Configuration of Mobile Ad Hoc Networks (Tayal
                   et al.)  . . . . . . . . . . . . . . . . . . . . . 14
         2.1.2.5.  No Overhead Autoconfiguration OLSR (Mase et
                   al.) . . . . . . . . . . . . . . . . . . . . . . . 15
         2.1.2.6.  PDAD-OLSR: Passive Duplicate Address Detection
                   for OLSR (Weniger et al.)  . . . . . . . . . . . . 17
         2.1.2.7.  Passive Duplicate Address Detection for
                   On-demand Routing Protocols (Jeong et al.) . . . . 19
         2.1.2.8.  Prophet Address Allocation for Large Scale
                   MANETs (Zhou et al.) . . . . . . . . . . . . . . . 21
     2.2.  Solutions for Connected MANET scenarios  . . . . . . . . . 23
       2.2.1.  No merging support . . . . . . . . . . . . . . . . . . 23
         2.2.1.1.  Automatic Configuration of IPv6 Addresses for
                   Nodes in a MANET with Multiple Gateways
                   (Ruffino et al.) . . . . . . . . . . . . . . . . . 23
         2.2.1.2.  Simple MANET Address Autoconfiguration
                   (Clausen et al.) . . . . . . . . . . . . . . . . . 24
         2.2.1.3.  Extensible MANET Auto-configuration Protocol
                   (EMAP) (Ros et al.)  . . . . . . . . . . . . . . . 26
         2.2.1.4.  Global Connectivity for IPv6 Mobile Ad Hoc
                   Networks (Wakikawa et al.) . . . . . . . . . . . . 28
         2.2.1.5.  Multihop Radio Access Network (MRAN) Protocol
                   Specification (Hofmann)  . . . . . . . . . . . . . 30
         2.2.1.6.  Automatic IP Address Configuration in VANETs
                   (Fazio et al.) . . . . . . . . . . . . . . . . . . 32
       2.2.2.  Merging support  . . . . . . . . . . . . . . . . . . . 34
         2.2.2.1.  Address Autoconfiguration in Optimized Link
                   State Routing Protocol (Adjih et al.)  . . . . . . 34
         2.2.2.2.  Extended Support for Global Connectivity for
                   IPv6 Mobile Ad Hoc Networks (Cha et al.) . . . . . 36
         2.2.2.3.  Gateway and Address Autoconfiguration for IPv6
                   Adhoc Networks (Jelger et al.) . . . . . . . . . . 38



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         2.2.2.4.  MANET Autoconfiguration using DHCP (Templin et
                   al.) . . . . . . . . . . . . . . . . . . . . . . . 39
   3.  Security Considerations  . . . . . . . . . . . . . . . . . . . 42
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 43
   5.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 44
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 45
     6.1.  Normative References . . . . . . . . . . . . . . . . . . . 45
     6.2.  Informative References . . . . . . . . . . . . . . . . . . 45
   Appendix A.  Change Log  . . . . . . . . . . . . . . . . . . . . . 48
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 49
   Intellectual Property and Copyright Statements . . . . . . . . . . 50








































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1.  Introduction and motivation

   Multi-hop communication in ad hoc networks presents some interesting
   advantages, where no permanent infrastructure is required.  Also, the
   coverage area of an existing infrastructure can be extended through
   multi-hop ad hoc communication.  Several MANET routing protocol
   specifications have been developed by the IETF MANET WG.  In order to
   allow wide deployment of ad hoc networks, in which IP routing is the
   most candidate approach, IP configuration of nodes is a strong
   requirement that need to be satisfied.  In this context, the AUTOCONF
   WG is working towards standard specifications and solutions for IP
   address autoconfiguration within different MANET environments.

   Ad hoc networks present particular characteristics that should be
   taken into account when designing address auto-configuration
   protocols.  Since existing solutions for IP infrastructure-based
   networks (e.g., RFCs 4861, 4862, 3315 etc.) were designed for a
   different scope that MANETs [1], there are several issues that need
   to be tackled, mainly (but not only) the following: the lack of
   multi-hop support, the lack of dynamic topology support, the lack of
   network merging support and the lack of network partitioning support.

   The main goal of the AUTOCONF WG is to develop solutions for IPv6
   address auto-configuration (both MANET-local and global scoped).  The
   group has identified two possible scenarios of MANET where IP address
   auto-configuration is required [1]:

   o  Standalone MANETs: these networks are not connected to any
      external network.  All traffic is generated by MANET nodes and
      destined to nodes in the same MANET.  Examples of these networks
      are conference networks, battlefield networks, surveillance
      networks, etc.  In this scenario, nodes may join or leave
      randomly.  Besides, most likely no pre-established nor reliable
      address or prefix allocation agency will be present in the
      network.

   o  Connected MANETs.  These networks have connectivity to one or more
      external networks, typically the Internet, by means of one or more
      gateways that are also known as MBRs (MANET Border Routers).
      These networks may be connected to the Internet in permanent
      fashion or in intermittent fashion.

   This draft aims at providing a survey on most of the previously
   proposed IP autoconfiguration solutions, trying to serve as a useful
   reference for the AUTOCONF WG during the problem space analysis and
   solution design phases.

   In the following section, we provide a description of several



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   existing AUTOCONF solution proposals, analysing them based on some
   evaluation considerations proposed in [2].  In order to present the
   analysed solutions in a structured way, two major classification
   levels are used: i) standalone/connected, and ii) partitioning/
   merging support.

   The given analysis conforms to the AUTOCONF problem statement draft
   [1] and the MANET architecture draft [3].











































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2.  IP address auto-configuration protocols

   In this section we briefly describe some of the existing proposals
   for IP address autoconfiguration, classifying them according to some
   of the evaluation considerations introduced in [2].

2.1.  Solutions for Standalone MANET scenarios

2.1.1.  No merging support

2.1.1.1.  IP address Autoconfiguration for Ad Hoc Networks (Perkins et
          al.)

   This address autoconfiguration mechanism -- proposed in [4] --
   basically consists in choosing an address randomly from an address
   pool (i.e., a network prefix) available to the MANET and then
   performing a Duplicate Address Detection procedure within the MANET.

   Assumptions: It is assumed that nodes performing this
   autoconfiguration protocol obtain a non-link-local prefix (it cannot
   be link-local, since the addresses have to be valid over a multiple-
   hop distance) from which to configure an address.  The method to
   obtain a globally routable prefix is not specified in the solution
   and, in case it is not possible to obtain any suitable one, a
   reserved IPv6 prefix, called MANET_PREFIX, is used: fec0:0:0:
   ffff::/64.

   Approach description: This solution basically works as follows: a
   node first selects a random address from the non-link-local prefix
   that is deployed in the MANET and then performs a Non-unique Address
   Detection procedure to check for its uniqueness across the MANET.  To
   perform this uniqueness check, the node sends an Address Request
   (AREQ) message, including the randomly chosen tentative non-link-
   local IP address.  This message is broadcast to its neighbours, by
   sending the message using the all-nodes multicast IPv6 address as
   destination of the packet.  The source address used by the node to
   send the AREQ message is another temporary IP address, acquired only
   for the purpose of sending these messages.  This temporary IPv6
   address belongs to a different non-overlapping prefix -- called
   MANET_INITIAL_PREFIX -- so the probability of this address to be
   duplicated in the network is very low, given its short lifetime (this
   address is only used in this message exchange and discarded
   thereafter).  When a node receives an AREQ message, it creates a
   reverse route entry for the temporary IPv6 address of the node.  If
   the tentative address contained in the AREQ message does not match
   the address of the receiving node, it rebroadcasts the message to its
   neighbours.  If the IP address of the receiving node matches the
   tentative address contained in the AREQ message it sends an Address



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   Reply (AREP) message to the sender, indicating that the address is
   already in use.  The route created by the AREQ messages is used to
   route the message back to the source node.

   A node waits for a certain amount of time after sending an AREQ
   message, for the reception of an AREP message.  The process is
   repeated if no answer is received, and if after a number of attempts
   no AREP has been received, the node assumes that the tentatively
   chosen IPv6 address is unique and starts using it.  The values
   configured for the involved timers and retry parameters have an
   impact on the maximum size of the MANET where the solution would
   properly work.  Additionally, since the Non-unique Address Detection
   procedure is performed only when the node initially chooses the
   tentative IPv6 address to use, this mechanism does not support
   merging of MANETs.

   AREQ and AREP are a modification of the standard ICMPv6 Neighbour
   Advertisement and Neighbour Solicitation messages, respectively.

   Based on [2], this solution has the following key features:

   o  MANET scenario: the solution targets standalone MANETs, although
      it considers the possibility of being applied to connected
      scenarios in those cases in which nodes are provided with the non-
      link-local prefix to be used in the MANET.

   o  Routing protocols' dependency: the solution is routing protocol
      independent.

   o  Address uniqueness: the proposed solution makes use of Non-unique
      Address Detection in the initial address assignment phase.

   o  Distributed/centralised approach: the solution does not make use
      of any centralised server.

   o  Merging support: the solution does not support merging.

   o  Prefix assignment support: the solution does not support the
      assignment of IPv6 prefixes to nodes.

   o  Protocol overhead: the solution requires additional message
      flooding (AREQ messages) to verify if an IP address is being used
      in the MANET.








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2.1.2.  Merging support

2.1.2.1.  IPv6 Autoconfiguration in Large Scale Mobile Ad-Hoc Networks
          (Weniger et al.)

   The solution described in [5] extends the Neighbour Discovery and
   IPv6 Stateless Address Autoconfiguration mechanisms to work in multi-
   hop wireless networks.

   Assumptions: The solution assumes a hierarchical approach, where
   there are two different types of participating nodes: those that
   obtain IPv6 addresses by using a modified version of IPv6 Neighbour
   Discovery, and special nodes -- called leader nodes --, that are
   responsible for parts of the address configuration of other nodes.

   Approach description: The solution basically extends IPv6 Neighbour
   Discovery to provide nodes within a multi-hop environment with IPv6
   address autoconfiguration capabilities.  To do so, the following
   modifications to the IPv6 Neighbour Discovery protocol are proposed:

   o  The Neighbour Solicitation message is modified to allow it to be
      broadcast to a bounded area of radius r_s hops (instead of only a
      single hop).  In addition, a new option for Neighbour Discovery is
      defined (called MANET option) which contains a Random Source ID
      (RS-ID) field, that is used to distinguish different nodes.  Nodes
      use the all-nodes multicast address instead of the solicited-node
      multicast address.  This mechanism guarantees link-local addresses
      to be unique within the scope (limited by r_s) of each node.

   o  To enable the configuration of unique site-local addresses, a
      hierarchy is established by special nodes (called leader nodes)
      that configure a group of nodes by issuing Router Advertisements
      (RA) within their scope, containing the subnet ID (i.e., network
      prefix) and its link-local address as source address.  The subnet
      ID has to be unique for each leader node, so Non-unique Address
      Detection has to be performed between the leader nodes within the
      entire Ad hoc network.  An algorithm is provided for the election
      of leader nodes.

   It should be noted that because of the nature of the solution, it
   would be possible to have multihomed nodes -- that is, nodes with
   more than one IPv6 address -- if a node is within the scope of more
   than one leader node.

   Based on [2], this solution has the following key features:

   o  MANET scenario: the solution targets standalone MANETs, although
      it could be possible to extend it to support the assignment of



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      global IPv6 addresses.

   o  Routing protocols' dependency: the solution does not depend on any
      particular ad-hoc routing protocol, but it may be advantageous the
      routing protocol it follows a hierarchical structure.  Besides, it
      is also preferable that nodes move in logical groups.  Otherwise,
      the cost of maintaining the hierarchical structure may be
      considerable.

   o  Address uniqueness: the proposed solution makes use of a periodic
      Non-unique Address Detection for ensuring the address uniqueness
      within the scope of the leader node.  Since each leader node makes
      use of a different Subnet ID, the uniqueness of the assigned
      address within the entire MANET is ensured.

   o  Distributed/centralised approach: the solution does not make use
      of any centralised server, but considers the existence of special
      nodes (leader nodes) that participate in the mechanism in a
      distributed fashion.

   o  Merging support: the solution support merging, by leader nodes
      performing periodic Non-unique Address Detection that ensures the
      uniqueness of Subnet IDs.

   o  Prefix assignment support: the solution does not support the
      assignment of IPv6 prefixes to nodes.

   o  Protocol overhead: the solution requires additional message
      flooding within a bounded area of radius r_s hops.

2.1.2.2.  Ad Hoc IP Address Autoconfiguration (Jeong et al.)

   The solution described in [6] proposes two Non-unique Address
   Detection mechanisms.  The first one -- called "strong DAD" -- is
   done in the initial phase when the ad hoc node does not have an IP
   address configured yet, it relates to the fact that before a randomly
   generated address is assigned and used, it should be verified that it
   will not create an address conflict.  On the other hand the second
   Non-unique Address Detection mechanism -- called "weak DAD" -- is
   always executed by nodes taking part in ad hoc routing in order to
   prevent any address conflicts due to mergers.

   Assumptions: The solution assumes that initially a random address is
   selected by ad hoc nodes using the reserved IPv6 prefix MANET_PREFIX.

   Approach description: This approach includes two different Non-unique
   Address Detection mechanisms:




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   o  Strong DAD: based on [4].  Strong DAD is done initially after an
      ad hoc node has chosen randomly an IP address and it is trying to
      find out whether there is a duplication conflict or not.  AREQ
      message for Strong DAD is broadcast in site-local scoped all node
      multicast address, IPV6_MANET_BROADCAST_ADDRESS.  The ad hoc node
      waits for an AREP message -- indicating the selected address has
      already been utilised -- until the timer for Strong DAD expires.
      In the case an AREP message arrives it chooses a new address and
      executes Strong DAD mechanism again. [6] describes the message
      format, using ICMPv6 messages (new types are defined). [7]
      describes the message format for AODV.

   o  Weak DAD: based on [8].  During ad hoc routing, weak DAD is used
      to find out whether address duplication, due to merging has
      occurred or not.  The concept of ``Virtual IP address'', which is
      the combination of an ''IP address'' and an ``Key'', is used,
      which is selected to be unique by each mobile ad hoc node.  This
      ''key'' is appended to control packets of ad hoc routing protocol,
      such as route discovery messages or hello messages.  Intermediate
      routing points must store the ''key'' value for each address in
      its routing table.  Using these ''keys'', duplication conflicts
      can be found out during ad hoc routing process.  An AERR message
      is sent during Weak DAD for the purpose of indicating that an
      address duplication happened.  The ad hoc node that receives an
      AERR message should autoconfigure a new IPv6 address through
      Strong DAD.  The same AERR message is used to inform each peer
      node that its address has been changed.  In order to keep ongoing
      sessions after an address duplication episode, data packets are
      sent to the new address through IP tunnelling.  The destination
      address in outer IP header is the new IP address of the node that
      announced duplicate address and the inner IP header contains the
      duplicate IP address of the node, i.e. the old address of the
      node.  The match duplicate address and new address is done in an
      Address Mapping Cache.

   Based on [2], this solution has the following key features:

   o  MANET scenario: the solution targets standalone MANETs.

   o  Routing protocols' dependency: the solution does not depend on any
      particular ad-hoc routing protocol.

   o  Address uniqueness: the proposed solution makes use of two
      different Non-unique Address Detection mechanisms.

   o  Distributed/centralised approach: the solution is distributed.  It
      does not make use of either any centralised servers or special
      nodes.



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   o  Merging support: the solution supports merging by looking for
      duplicate addresses on an ongoing basis.

   o  Prefix assignment support: the solution does not support the
      assignment of IPv6 prefixes to nodes.

   o  Protocol overhead: The Strong DAD mechanism requires additional
      message flooding (AREQ messages) to find out whether there is a
      duplication conflict or not.  The Weak DAD mechanism introduces
      also some protocol overhead since the Key extension (20 bytes) is
      appended to each control packet of the ad hoc routing protocol.

2.1.2.3.  IP Address Assignment in a Mobile Ad Hoc Network (Mohsin et
          al.)

   This proposed solution [9] is based on a dynamic allocation of IP
   addresses in MANETs using the concept of binary split.  A proactive
   approach is used, in the sense that each node can independently
   assign a new IP address without consulting any other node in the
   network.  Partitioning and merging as well as nodes abrupt departures
   are supported in this solution.

   Assumptions: It is assumed that all nodes collectively perform the
   DHCP functionality; where each node is capable of configuring a new
   node and providing it with a new IP address.  It is also assumed that
   one MANET node have the entire pool of IP addresses at the beginning.

   Approach description: In this proposed solution the concept of Buddy
   Systems is used.  This is a type of segregated lists used in memory
   allocation and supports efficient splitting and coalescing.  In the
   context of the proposed solution, binary buddies are used, where all
   buddy sizes are a power of two, and each size is divided into two
   equal parts.  Thus, every node has a disjoint set of IP addresses
   that it can assign to a new node without consulting any other node in
   the network.  When a new unconfigured mobile node (B) joins the
   network, it requests the nearest neighbour (A) an IP address.  Node
   (A) divides its IP address set into two, giving one half to the
   requesting node (B).  The new node assigns itself an IP address from
   the acquired pool of addresses, storing the rest of addresses to
   configure other nodes afterwards.  The new node (B) is now configured
   and is considered as the Buddy of node (A).  The scheme of the IP
   address assignment can be seen as a handshaking protocol between the
   server and the client, where the node requesting the IP address is
   considered as the client node and the node that actually assigns the
   IP address is considered as the server node.

   Nodes synchronise the IP blocks which they store to keep track of the
   assigned IP addresses and detect any IP leakage, where every node



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   keeps a record of all the IP address blocks in the network by
   maintaining a corresponding table.  Each node sends its IP address
   pool to all other nodes in the network, and each node receiving an IP
   pool from another node records the received information in its IP
   address table.  Through this approach, the network has among its
   nodes the available IP addresses organised in the form of a binary
   tree with a division of two identical blocks (Buddies) per level.

   Two mechanisms are proposed for releasing the node's IP address pool
   when the node leaves the network: i) graceful leave, in which the
   leaving node gives its IP address pool to any nearby node.  This
   nearby node may keep the IP address pool for itself or may search in
   its IP address table the Buddy of the leaving node and forward to it
   the IP pool. ii) abrupt leave, in which the node leaves with its IP
   address pool that leads to IP leakage.  In such a case, a pool of IP
   addresses that is not assigned to any node is not available.  IP
   leakage is detected from the IP address table stored at each node.
   Each node scans from time to time its IP address table for the IP
   pool of its Buddy node, if it does not find it, it concludes that the
   node has left and it merges this missing IP block to itself.

   Based on [2], this solution has the following key features:

   o  MANET scenario: This proposed solution targets standalone MANETs.

   o  Routing protocols' dependency: This proposed solution is
      independent of the underlying routing protocol.

   o  Address uniqueness: The proposed solution does not use any Non-
      unique Address Detection mechanism.

   o  Distributed/Centralised approach: Although this solution is based
      on IP address pools assignment and splitting, it has a distributed
      approach, where all nodes collectively perform the functionality
      of a DHCP server.

   o  Merging support: Thanks to employing the buddy systems, the
      proposed solution supports merging.  In case of merging, the
      process of buddies splitting allows the merging node to be
      assigned an IP address and an IP pool.

   o  Prefix assignment support: the solution does not support the
      assignment of IPv6 prefixes to nodes.

   o  Protocol overhead: the solution requires a kind of flooding so
      that each node sends its IP address block to all other nodes in
      the network.  Furthermore, other control messages are required in
      the form of request-reply messages to enable a new joining node to



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      be assigned an IP address, or in the form of announcement in the
      case of IP release.

2.1.2.4.  An Address Assignment for the Automatic Configuration of
          Mobile Ad Hoc Networks (Tayal et al.)

   The solution described in [10] is very similar to the previous one
   ([9]), sharing the idea (also used by others) of nodes assignment of
   half of their address pools to newly arrived nodes that request IP
   addresses.

   Assumptions: It is assumed that initially there is one node that
   configures itself as initiator node (when there is no other node in
   the network), configuring itself with a default IP address and
   starting to manage a default address pool.

   Approach description: The solution basically works as follows: when a
   new node i (called requester node) is willing to join the MANET, it
   has to contact an existing node j in the network.  If node j has the
   address pool, it divides it into two parts and allocates one part to
   node i.  The starting address of the allocated pool is the address of
   node i.  In case node j does not have the address pool, j starts
   searching for nodes that might have an address pool, by broadcasting
   a message (called SEARCH_ADDR).  The search message is forwarded by
   all the nodes which do not have an address pool.  A node receiving
   the search message, either replies with the address pool or with
   negative ACK.  If a node replies with its address pool, it marks half
   of its addresses as under allocation and wait for a POOL_ACCEPTED
   message from node j.  Node j replies with POOL_ACCEPTED message to
   the node whose address pool it received first, and allocates the
   received address pool to node i.

   This solution defines mechanisms to handle different scenarios, such
   as network partitioning and merging, message loss, etc.  More details
   can be found in [10].

   Based on [2], this solution has the following key features:

   o  MANET scenario: This proposed solution targets standalone
      scenarios.

   o  Routing protocols' dependency: This proposed solution is
      independent of the underlying routing protocol.

   o  Address uniqueness: The proposed solution does not use any Non-
      unique Address Detection mechanism, since the uniqueness of the
      solution is based on the split of the initially available IP
      address pool.



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   o  Distributed/Centralised approach: the solution is based on IP
      address pools assignment and splitting, where all nodes
      collectively perform the functionality of assigning addresses to
      newcomers.

   o  Merging support: the solution defines a mechanism to detect
      merging, through redistributing information about assigned
      addresses and pools.  If an address collision is detected, then
      the solution defines a mechanism to solve that, based on giving
      up/shrinking the address pool used by one of the nodes detecting
      the conflict.

   o  Prefix assignment support: Since the solution supports the
      assignment of address pools, it can be possible to use it to
      assign prefixes to nodes, although it is not explicitly covered by
      the mechanism.

   o  Protocol overhead: the solution requires some message flooding to
      search nodes that have an address pool available.

2.1.2.5.  No Overhead Autoconfiguration OLSR (Mase et al.)

   This solution [11] proposes some passive Non-unique Address Detection
   techniques to be used in MANETs running the OLSR protocol.  It
   utilises the Passive Duplicate Address Detection concept [12], [13],
   which enables nodes to passively detect duplicate addresses in the
   network (e.g., occurring after network merging) by analysing received
   routing protocol messages.  The basic idea of PDAD is to exploit the
   fact that some protocol events occur in case of duplicate address,
   but (almost) never in case of a unique address.  The proposed
   techniques may be used to ensure uniqueness of an address when it is
   initially generated before being assigned to an interface and the
   solution also performs to ensure uniqueness of addresses which have
   been assigned and used, and then a network merger happens.

   This is one of the multiple drafts proposing the use of PDAD for OLSR
   [14], [15].

   Assumptions: The protocol assumes the existence of a Non-unique
   Address Detection-based IP address generation mechanism.

   Approach description: The solution proposes an ongoing duplicate
   address detection mechanism, checking for inconsistencies in the
   routing protocol messages to diagnose duplicate address detection.
   The first kind of inconsistency is based on information included in
   OLSR messages (such as HELLO messages and TC messages) and the second
   kind of inconsistency is based on sequence numbers (when two nodes --
   which selected the same IP address -- are present in a network, they



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   would send control messages that will be inconsistent).

   Different Non-unique Address Detection rules -- twelve in total --
   are proposed to handle the cases where the distance between
   conflicting nodes is one hop, two hops and, three hops or more.  In
   the two first cases the detection is done by means of HELLO messages
   and in the last case -- three hops or more -- the detection is
   fulfilled by using information inside TC messages.  Also, an
   additional case is taken into account: this is a specific multihop
   address conflict case, where the address conflict results in
   deficiencies in the MPR selection.

   Each node has an "autoconfiguration state".  This state is an
   indicator of how long the node has been in the network.  The central
   idea, is that each time a node generates a tentative address, it
   should enter the network gradually, running a restrained version of
   the OLSR protocol.  In this way, the node can detect which addresses
   are being used, checking for duplicates of its own address, while
   avoiding to disrupt the routing tables of the other nodes, in the
   event that its address is actually found to be in conflict.

   Based on [2], this solution has the following key features:

   o  MANET scenario: This Non-unique Address Detection technique is to
      be used in standalone MANETs.

   o  Routing protocols' dependency: this mechanism depends on OLSR,
      since the Non-unique Address Detection technique is designed for
      MANETs running the OLSR protocol.

   o  Address uniqueness: The proposed mechanism assumes the existence
      of a Non-unique Address Detection-based address assignment
      mechanism.

   o  Distributed/centralised approach: the proposed solution follows a
      distributed approach given that all nodes have the same
      responsibility detecting address conflicts.

   o  Merging support: The proposed solution supports merging, enabling
      nodes to continuously detect duplicate addresses by analysing
      received routing protocol messages.

   o  Prefix assignment support: the solution does not support the
      assignment of IPv6 prefixes to nodes.

   o  Protocol overhead: the proposed mechanism does not add any
      additional messages but it checks for inconsistencies in the
      routing protocol messages to diagnose duplicate address detection.



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2.1.2.6.  PDAD-OLSR: Passive Duplicate Address Detection for OLSR
          (Weniger et al.)

   This solution [14] proposes a passive Non-unique Address Detection
   mechanism for configured address uniqueness maintenance in MANETs
   running the OLSR protocol.

   Assumptions: The protocol assumes the existence of a Non-unique
   Address Detection-based address generation mechanism.

   Approach description: The proposed solution is made up of a set of
   algorithms which specify how to detect duplicate addresses based on
   incoming routing protocol messages.  The algorithms utilise different
   parameters in TC and HELLO messages such as link states (i.e.,
   neighbour interface addresses), link codes, (message) sequence
   numbers, and addresses in OLSR routing protocol messages as well as
   addresses in the IP header.  PDAD-OLSR allows the detection of
   conflicts by intermediate nodes that have unique addresses.

   Each node conceptually maintains two tables for PDAD: a Last received
   Protocol Messages (LRM) table and a Neighbour History (NH) table.
   LRM table contains information about the last TC and HELLO protocol
   message received from a specific originator address (e.g., originator
   address, message type, sequence number, neighbour interface
   addresses, receive time).  NH table contains the history of
   neighbouring node addresses and is built from received HELLO messages
   (e.g., neighbour interface address, last time the receiver has
   selected this neighbour interface address as MPR, Last time the
   receiver has been selected as MPR by this neighbour interface
   address, reception time).

   The solution proposes eight different algorithms for conflict
   detection:

   o  PDAD-Source Address (SA).  Whenever a node receives a TC or HELLO
      message, it compares the source address in the IP header to its
      own address (the IP source address is always the address of the
      last forwarder).  This mechanism (e.g., Both addresses coincide)
      allows nodes to detect conflicts with its neighbouring nodes.

   o  PDAD-Sequence Numbers (SN): If a node receives a TC or HELLO
      message, it compares the originator address with its own address.
      If they are equal and the sequence number in the message is higher
      than the receiver's sequence number, a conflict of the originator
      address is detected.  This mechanism allows to detect conflicts
      between nodes that are any number of hops away from each other.





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   o  PDAD-Sequence Number Difference (SND): If a node receives a TC or
      HELLO message, it compares the sequence number in the message with
      the sequence number in the previously received message from the
      same originator address and with the same message type (there is a
      relation between the time a node has originated two TC messages
      and the sequence number in those TC messages).  This mechanism
      allows to detect conflicts between nodes that are any number of
      hops away from each other.

   o  PDAD-Sequence Numbers Equal (SNE): If an intermediate node
      receives a TC or HELLO message, it searches its LRM table for a
      message with the same type value and the same tuple < sequence
      number, originator address > (the tuple < sequence number,
      originator address > uniquely identifies messages originated by a
      specific node.  This mechanism allows to detect conflicts between
      nodes that are any number of hops away from each other.

   o  PDAD-SNs Always Increment (SNI): If a node receives a HELLO
      message, it compares the sequence number in the message with the
      sequence number in the previous HELLO message from the same
      originator address (HELLO messages sent by a specific node are
      received in the order they are sent).  This mechanism only allows
      to detect conflicts between nodes that are at most two hops away
      from each other.

   o  PDAD-Neighbourhood History (NH): If a node receives a TC message,
      it checks whether its own address is part of the neighbour
      interface addresses in the TC message.  If this is the case and
      the link code indicates a bi-directional link, the node searches
      the originator address in its NH table (a TC message only contains
      neighbours that have selected the originator address as MPRs and
      that requires a bi-directional link).  This mechanism allows to
      detect conflicts between nodes that are any number of hops away
      from each other.

   o  PDAD-Link States (LS): If a node receives a TC message with its
      own address as originator address, it searches in its NH table for
      each of the neighbour interface addresses (if the message has been
      originated by the receiver, it must only contain addresses of
      recent neighbour interfaces).  This mechanism allows to conflicts
      between nodes that are any number of hops away from each other.

   o  PDAD-extended Neighbourhood History (eNH): If a node receives a TC
      message, it checks for each neighbour interface address in the
      message if it is a neighbour.  This algorithm is basically the
      PAD-NH algorithm executed on behalf of a neighbouring node.
      Minimal additional signalling is needed.  This mechanism allows to
      detect conflicts between nodes that are any number of hops away



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      from each other.

   For some of the above mechanisms it is crucial to detect a possible
   sequence number wrap-around, so a mechanism to detect this kind of
   events is proposed.

   Based on [2], this solution has the following key features:

   o  MANET scenario: The solution targets standalone MANETs.  Although
      it proposes a Non-unique Address Detection mechanism suitable for
      any kind of addresses exchanged in routing protocol messages, be
      it MANET-local or globally routable addresses, the solution does
      not address the issue of how to obtain global IPv6 addresses.

   o  Routing protocols' dependency: this solution requires OLSR, since
      the set of proposed techniques are applicable to MANETs running
      the OLSR protocol.

   o  Address uniqueness: The proposed mechanism assume the existence of
      an address assignment mechanism which may assign duplicate
      addresses.

   o  Distributed/centralised approach: The solution follows a
      completely distributed approach, every node has the same
      responsibility in detecting duplicate addresses and does the same
      processing.

   o  Merging support: The proposed solution supports merging given that
      it enables nodes to continuously detect duplicate addresses in the
      network by analysing received routing protocol messages.

   o  Prefix assignment support: the solution does not support the
      assignment of IPv6 prefixes to nodes.

   o  Protocol overhead: the solution enables nodes to passively detect
      duplicate addresses in the network by analysing received routing
      protocol messages and thus does not cause any overhead.

2.1.2.7.  Passive Duplicate Address Detection for On-demand Routing
          Protocols (Jeong et al.)

   This solution [16] proposes a set of Non-unique Address Detection
   techniques to be used jointly with an on-demand routing protocol.  In
   this proposal passive duplicate address detection is performed by
   analysing incoming on-demand routing protocol packets.

   Assumptions: The protocol assumes the existence of an on-demand
   routing protocol and a Non-unique Address Detection-based IP address



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   configuration mechanism.

   Approach description: In this proposal passive duplicate address
   detection is performed by analysing incoming on-demand routing
   protocol packets.  Additional information included in routing
   protocol packets allows end-points of a communication -- source or
   destination -- to detect that the other end-point is using an address
   which is duplicated in the MANET.

   This additional information is included into routing control packets
   exchanged for route discovery and it may be: the node location when
   it configured its IP address, the node's neighbour list when it
   configured its IP address, or a sequence number in RREP packets
   (increased whenever a destination node sends a new RREP packet).

   The authors propose different mechanisms for detecting address
   conflicts:

   o  PDAD-RREQ-with-Location-information Technique (RQL): This
      technique includes location information in RREQ packets to
      differentiate between RREQ packets which contain the same source
      address but are generated by different nodes.

   o  PDAD-RREQ-with-Neighbour-knowledge Technique (RQN): This technique
      includes a list of neighbour nodes (this list is captured and
      recorded when the node's IP address is configured) in RREQ packets
      to differentiate between RREQ packets which contain the same
      source address but are generated by different nodes.

   o  PDAD-RREP-with-SEQ Technique (RPS) : This technique requires an
      incremental PDAD-sequence number to be included in each RREP
      packet transmitted by a destination node.  Therefore, when a
      source node receives more than one RREP packet with the same PDAD-
      sequence number and the same destination address, the source node
      can detect the address conflict of destination nodes.

   o  PDAD-RREP-with-Location-information Technique (RPL): This
      technique includes location information into RREP packets to
      differentiate between RREP packets which contain the same source
      address (the source address of RREP packets is the destination
      address of RREQ packets) but are generated by different nodes.

   o  PDAD-RREP-with-Neighbour-knowledge Technique (RPN): When a
      destination node replies with an RREP packet, a list of neighbour
      nodes of the destination node (this list is captured and recorded
      when the node's IP address is configured) is included in the RREP
      packet.




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   The document does not include how to perform address conflict
   resolution.

   Based on [2], this solution has the following key features:

   o  MANET scenario: The solution targets standalone MANETs.  Although
      the proposed Non-unique Address Detection mechanism is suitable
      for any kind of addresses exchanged in routing protocol messages,
      be it MANET-local or globally routable addresses, it does not
      define any mechanism to obtain global IPv6 addresses.

   o  Routing protocols' dependency: The set of proposed techniques
      supposes the existence of an on-demand ad-hoc routing protocol.

   o  Address uniqueness: The proposed mechanism assumes the existence
      of a Non-unique Address Detection-based address assignment
      mechanism.

   o  Distributed/centralised approach: The solution follows a
      completely distributed approach, every node has the same
      responsibility in detecting duplicate addresses and does the same
      processing.

   o  Merging support: The proposed solution supports merging given that
      it enables nodes to continuously detect duplicate addresses in the
      network by analysing received routing protocol messages.

   o  Prefix assignment support: the solution does not support the
      assignment of IPv6 prefixes to nodes.

   o  Protocol overhead: the solution enables nodes to passively detect
      duplicate addresses in the network by analysing received routing
      protocol messages and thus does not cause any overhead.

2.1.2.8.  Prophet Address Allocation for Large Scale MANETs (Zhou et
          al.)

   The mechanism defined in [17] is based on the use of a special type
   of function to derive the IPv6 addresses of nodes, so the probability
   of address duplication is very low, and therefore the use of a Non-
   unique Address Detection mechanism can be avoided.

   Assumptions: This solution is based on the use of a stateful function
   f(n) (where the initial state of f(n) is the seed) that produces as
   output an integer sequence of numbers.  Different seeds lead to
   different sequences, and the state of f(n) is updated.  This function
   can be used to generate IP addresses, since it satisfies the
   following properties:



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   o  The interval between two occurrences of the same number in a
      sequence is extremely long.

   o  The probability of more than one occurrence of the same number in
      a limited number of different sequences initiated by different
      seeds during some interval is extremely low.

   These properties may be satisfied if the space of available addresses
   is large, so it is relatively easy to achieve in IPv6.

   Approach description: The mechanism basically work as follows: the
   first node in the MANET chooses a random number as its IP address and
   uses a random or default state value as the seed for its f(n).  When
   a different node approaches, the first node uses its f(n) to obtain a
   different number and state.  This number is used by the second node
   as its IP address, and the state is used as the seed for its f(n).
   After that both nodes are able to assign IP addresses to other nodes.

   Authors of the mechanism propose different mechanisms to support
   partitioning/merging, such as for example including the seed used in
   the MANET in the messages of the routing protocol.  By doing that,
   nodes of different merging MANETs can easily detect the merge (if
   different seeds are received, that would mean that a merge has
   happened) and start checking if there are potential IP address
   conflicts.  Given the characteristics of the function f(n) if a MANET
   gets partitioned and later merges, IP address conflicts are very
   unlikely to occur.

   Based on [2], this solution has the following key features:

   o  MANET scenario: the solution targets standalone MANETs.

   o  Routing protocols' dependency: the solution is routing protocol
      independent.

   o  Address uniqueness: the proposed solution does not define any Non-
      unique Address Detection mechanism.  The address uniqueness is
      ensured by using a "prophet" allocation with a very low
      probability of collision.

   o  Distributed/centralised approach: the solution does not make use
      of any centralised server.

   o  Merging support: the solution proposes different mechanisms to
      support merging.

   o  Prefix assignment support: the solution supports the assignment of
      IPv6 prefixes to nodes, by using the DHCP prefix delegation.



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   o  Protocol overhead: only few additional messages are required to
      assign addresses to new nodes.

2.2.  Solutions for Connected MANET scenarios

2.2.1.  No merging support

2.2.1.1.  Automatic Configuration of IPv6 Addresses for Nodes in a MANET
          with Multiple Gateways (Ruffino et al.)

   This proposed solution [18] describes a mechanism enabling nodes
   belonging to a MANET connected to the infrastructure -- by means of
   one or more gateways -- to obtain global IPv6 addresses that could be
   used to communicate with external nodes.

   Assumptions: This mechanism assumes the existence of one or more
   gateways that provide MANET nodes with connectivity to external
   networks (e.g., the Internet).  It is also assumed that nodes running
   this solution obtain at the bootstrapping phase a MANET local IPv6
   address (which is the address that the node uses when it participates
   in the routing protocol, which is assumed to be OLSR).  The
   uniqueness of the obtained address should be ensured by means of a
   Non-unique Address Detection method.  Neither the procedure followed
   to obtain this address, nor the Non-unique Address Detection method
   used to check its uniqueness, are defined in this solution.

   Approach description: The mechanism basically works as follows: at
   bootstrap, a node configures a Primary Address (PADD) that is MANET-
   scoped and is used as main address in OLSR messages.  The node then
   is able to start participating to OLSR and receiving topology
   information.  Each of the gateways available at the MANET has a
   global IPv6 prefix that is announced using a new OLSR message type,
   called Prefix Advertisement (PA).

   With the prefix information received in the PA messages, a node is
   able to build a set of global IPv6 addresses (called Secondary
   Addresses: SADDs).  Among them, the node chooses the "best" prefix
   and starts using the address formed from this prefix (called,
   Designated Secondary Address: DSADD).  The node introduces all (or a
   subset) of the SADDs (including the DSADD) in OLSR messages and
   starts broadcasting them, enabling these addresses to be routable and
   reachable within the MANET.  It should be noted, that this solution
   does not define any new Non-unique Address Detection mechanism, while
   it is suggested to use a generic MANET Non-unique Address Detection
   procedure, such as [4], to verify the uniqueness of MANET-local and
   global addresses.

   Based on [2], this solution has the following key features:



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   o  MANET scenario: the solution targets connected MANETs.

   o  Routing protocols' dependency: the solution requires OLSR to be
      run in the network.

   o  Address uniqueness: the proposed solution does not define any Non-
      unique Address Detection mechanism, although requires some generic
      one to be used to ensure the uniqueness of MANET-local and global
      addresses.

   o  Distributed/centralised approach: the solution does not make use
      of any centralised server, but requires gateways to announce the
      global IPv6 prefixes that can be used by MANET nodes in the
      configuration of their IPv6 addresses.

   o  Merging support: the solution partially supports merging, since
      the scenario in which new gateways join the network as a result of
      a merger is considered.  However, since no Non-unique Address
      Detection mechanism is defined, the solution does not describe how
      to deal with IPv6 address duplication after merging of different
      MANETs.

   o  Prefix assignment support: the solution does not support the
      assignment of IPv6 prefixes to nodes.

   o  Protocol overhead: the solution adds some overhead. since Gateways
      broadcast prefix information.

2.2.1.2.  Simple MANET Address Autoconfiguration (Clausen et al.)

   This proposed solution [19] aims to provide a simple IP
   autoconfiguration mechanism for mobile nodes joining an existing
   MANET.  This mechanism is designed for MANETs that act as an edge-
   extension to the Internet, where mobile nodes need to maintain the
   connections with each other and with the Internet.

   Assumptions: It is assumed that at least one node in the network is
   already configured with a permanent address.  In the absence of a
   configured node, it is assumed that an election mechanism is
   undertaken allowing a selected node to be self-configured.

   Approach description: In this proposed solution, only configured
   nodes can participate in the MANET and are considered as MANET nodes.
   These nodes are also considered as "configuring nodes" aiding the new
   joining nodes to acquire an IP address.  Actually, each new joining
   node is firstly assigned a temporary local address then a permanent
   global address.  The configuring nodes emit periodical ADDR_BEACON
   messages to their neighbours in order to signal their existence to



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   new nodes.  A new node joining the network selects a configuring node
   from its neighbours, then sends an Address Request (AREQ) to this
   selected configuring node and waits for a reply.  The process of
   sending AREQ may be repeated for a number of trials until either
   receiving a reply or selecting a new configuring node.  The
   configuring node replies by an Addr-Config message, containing a
   local temporary address, and keeps track of the link existence with
   the new joining node through local routing messages exchange on this
   link.  If this link disappears then the configuring node gives up,
   otherwise the configuring node assigns a global address to the new
   joining node.

   The process of obtaining a temporary address consists of having an
   address space, where each MANET node independently selects an address
   sequence from this space and signals it to its neighbours (through
   beacons).  Each MANET node records the address sequence received from
   is neighbours to avoid conflicts in the chosen addresses.  If a
   conflict is detected between two nodes, the node with the lowest ID
   should select a new sequence if both nodes are not configuring nodes
   (MANET nodes that are not yet engaged in configuring a new node).
   Otherwise, if one or more configuring nodes are involved in the
   conflict, each configuring node should narrow its sequence of
   addresses to contain only the address that is currently assigned (in
   order to keep on the configuring session).  On the other hand two
   options exist for global addresses allocation.  One option is that
   the configuring node acts as a modified DHCP proxy and transmits a
   request to a DHCP server to acquire a global address for each new
   node it configures.  Another option is that the configuring node
   consults the nodes' topology tables (containing destinations and thus
   network addresses), and then picks up an unused address.  It then
   sends an advertisement to all MANET nodes to be sure that this
   address is not used.  If a node detects that its address is being
   used, it can signal the conflict to the originator of the
   advertisement.

   Based on [2], this solution has the following key features:

   o  MANET scenario: This proposed solution targets connected MANET
      scenarios.

   o  Routing protocols' dependency: This proposed solution uses OLSR,
      typically extending OLSR messages, however it is not dependent on
      the routing protocol.  Although the proposed solution is open to
      any routing protocol, the fact that periodical beacons are used
      requires a proactive routing protocol.

   o  Address uniqueness: The proposed solution uses a Non-unique
      Address Detection mechanism to avoid conflicts in IP address



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      assignment.  In global address allocation, using a Non-unique
      Address Detection mechanism is an option but the proposed solution
      can function without a Non-unique Address Detection mechanism if
      the modified DHCP proxy approach is followed.  While in temporary
      address allocation, a limited Non-unique Address Detection
      mechanism is used with the neighbourhood to resolve any conflict
      when assigning temporary addresses sequences to MANET nodes.

   o  Distributed/Centralised approach: The proposed solution is
      distributed in the sense that it can employ a decentralised DHCP
      server using the concept of proxy DHCP to reach the server.

   o  Merging support: This proposed solution has no merging support.

   o  Prefix assignment support: The proposed solution allows prefix
      assignment through using DHCP.

   o  Protocol overhead: the solution requires a considerable number of
      signalling.  This is mainly during the advertisement messages for
      global addresses flooded to all nodes in the network for verifying
      the global address uniqueness, the periodical ADDR_BEACON messages
      that are transmitted by each configuring nodes to its neighbours,
      and the Beacon messages signalling the selected address space by
      each configuring node during the process of temporary address
      assignment.  Furthermore, AREQ messages are used by each new
      joining node while communicating a neighbour configuring node,
      which in turn replies by an Addr-config message.

2.2.1.3.  Extensible MANET Auto-configuration Protocol (EMAP) (Ros et
          al.)

   The Extensible MANET Auto-configuration Protocol (EMAP) [20] provides
   an autoconfiguration solution for isolated as well as hybrid MANETs.
   EMAP is envisioned to be integrated within unicast routing protocols
   as DYMO or OLSRv2.  The notion of intermediate proxies is used in the
   autoconfiguration process.  The general EMAP framework may be used as
   a service discovery protocol for MANETs, however the approach is
   extensible to other services.  An optional feature in EMAP includes
   DNS discovery, where nodes can discover DNS servers reachable from
   the MANET, and this feature can be extended to services like SIP,
   proxies, and authentication entities.

   Assumptions: It is assumed that at least one element must act as a
   gateway between the MANET and the fixed network.  This element is
   called an Internet Gateway (IGW).

   Approach description: EMAP allows MANET nodes to configure unique IP
   local addresses and globally routable IP addresses.  The local



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   configuration allows a MANET node to communicate with other nodes in
   the same MANET.  To configure a local address, the MANET node picks
   an IP address and asks the network if it is already being used, thus
   avoiding address duplication.  In this process, a node generates a
   pair of IP addresses: temporary and tentative ones.  The temporary
   address is used as the originator-address, where it can be a mobile
   IP home address or another sort of highly likely unique address.
   While the tentative address is the one which is being requested and
   is used as the requested address in the DAD_REQ messages and the
   originator-address in DAD_REP messages.  Thanks to the proxy
   functionality, intermediate nodes can also answer with a DAD_REP
   message if they do not own the requested address but they do know
   that it is being used by another node.  If the MANET node sending the
   DAD_REQ receives no DAD_REP messages, then it understands that there
   is no address conflict and it considers that the tentative address is
   its local address.

   On the other hand, global configuration takes place through using the
   Internet Gateway (IGW), which may be a fixed element belonging to
   each network, or a mobile one which detects the presence of an
   attachment point to the Internet (e.g. a wireless router).  The
   mobile node requesting a global address either waits for
   advertisements sent by the IGW (mainly advertising its prefix) to
   configure its global address or floods a global configuration request
   (GC_REQ) message.  When an IGW receives a GC_REQ message, it sends a
   global configuration reply message (GC_REP) to the originator-address
   through unicast.  Thus, the originating node is able to auto-
   configure a global address by substituting the first bits of the
   requested local address by the prefix advertised by the IGW.  When
   there are multiple IGWs announcing their own information, the MANET
   node selects one, and the selection rules are implementation-
   dependent.

   A given option in EMAP allows a MANET node to issue a query to find
   DNS Server Advertisers, which provide IP addresses of available DNS
   servers.  This feature may be quite useful in situations where a high
   degree of auto-configuration is desired.

   Based on [2], this solution has the following key features:

   o  MANET scenario: This proposed solution is designed for standalone
      MANETs and connected MANETs.

   o  Routing protocols' dependency: Although EMAP is envisioned to be
      integrated with unicast routing protocols like DYMO or OLSRv2, it
      may be implemented as a standalone daemon.





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   o  Address uniqueness: The proposed solution uses a Non-unique
      Address Detection mechanism during the autoconfiguration of MANET
      local addresses.

   o  Distributed/Centralised approach: The proposed solution is a
      distributed solution in the sense of not being based on any DHCP
      servers.

   o  Merging support: No special merging mechanisms are explained in
      this solution.  However, no in-service Non-unique Address
      Detection is used which makes the merging support not feasible.

   o  Prefix assignment support: This solution employs IPv6 prefixes,
      where gateway nodes are responsible for advertising their
      prefixes.

   o  Protocol overhead: the solution adds certain overhead, depending
      on the network size, the number of IGWs, and the applied option in
      global address configuration.  The resulting overhead in this
      solution mainly concerns: flooding of the local address selected
      by each joining node to verify its uniqueness through the DAD_REQ
      messages, prefix advertisement by IGWs during global address
      configuration (this has more impact on the overhead when the
      number of IGWs increases), and flooding of GC_REQ messages by the
      node requesting a global address (in case that no prefix
      advertisement is taking place by the IGWs) where in this case
      GC_REP messages are sent by IGWs through unicast.  Furthermore,
      DAD_REPLY messages could take place in case of address conflicts
      detection.

2.2.1.4.  Global Connectivity for IPv6 Mobile Ad Hoc Networks (Wakikawa
          et al.)

   The solution described in [21] proposes how to provide Internet
   connectivity with mobile ad hoc networks.  It describes how to obtain
   a globally routable IPv6 address from an Internet gateway.  The
   Internet access method is not dependent on a particular MANET routing
   protocol, however there is still a need to a protocol.

   Assumptions: The solution assumes that before configuring a global
   IPv6 address, the node has configured a routable address (i.e.
   MANET-local address or a Mobile IPv6 home address).  The routable
   address is used for initial configuration when a node boots up and
   joins the MANET.

   Approach description: This mechanism [21] is similar to [22] from the
   point of view of how IPv6 addresses are configured.  Global prefix
   information is obtained from Internet gateways.  Two methods are



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   proposed for the Internet gateway discovery: one method periodically
   disseminates gateway advertisements to all nodes in the MANET; the
   other method utilises solicitation and advertisement signalling
   between a MANET node and the gateway.  Extended router solicitation
   and advertisements of the Neighbour Discovery Protocol (NDP) or
   extended control message of each MANET routing protocol can be used
   for this signalling.  The proposed methods target all MANET protocols
   regardless of whether they are reactive or proactive.  Internet
   gateways supply their own global prefix information and IPv6 global
   address to MANET nodes somehow, either proactively or reactively.  In
   this way, the reactive and proactive route discovery features of each
   MANET routing protocol are not disturbed.  An advertisement from the
   Internet gateway provides prefix information -- IP routing prefix and
   prefix length -- and lifetime.

   After accepting an advertisement from the Internet gateway inserts
   the Internet gateway address as an Internet route and the MANET node
   configures a global address from the prefix of the Internet gateway.
   It uses the 64-bit interface ID in order to construct a valid address
   with the acquired prefix.  It is assumed that before configuring a
   global IPv6 address, the node has configured a routable local address
   (i.e.  MANET-local address), and a Non-unique Address Detection
   mechanism has been performed for that routable local address (e.g.
   using the mechanism defined in [4] and [23]), so it is assumed that
   the global address would be also unique.  If not, the node may
   perform another Non-unique Address Detection mechanism for this
   global address.

   If the destination of a packet is inside the MANET even though a
   global routable address is used as destination address, the gateway
   prevents this packet from being forwarded to the Internet.  It
   returns the packet back to the MANET if it has a MANET route for the
   destination.  The source node receives an ICMP Redirect message from
   the Internet Gateway warning that it should use a host route (MANET-
   local address) instead of a default route (Internet route).  To do
   so, each Internet gateway may manage a list of IP addresses of all
   the associated MANET nodes (mainly if a reactive ad hoc routing
   protocol is being used).  So, each MANET node must contact the
   Internet gateway at least once it establishes an Internet route
   through the Internet Gateway in order to communicate its global
   routable address to the Internet Gateway.

   Based on [2], this solution has the following key features:

   o  MANET scenario: the solution targets connected MANETs.

   o  Routing protocols' dependency: Not restricted to any particular ad
      hoc routing solution, and it is designed to work properly with



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      both proactive and reactive protocols.

   o  Address uniqueness: It is assumed that the global address would be
      also unique.  If not, the node may perform a Non-unique Address
      Detection mechanism for this global address.  In any case the Non-
      unique Address Detection mechanism is considered out of scope.

   o  Distributed/centralised approach: The proposed solution uses a
      distributed approach where nodes do not solicit any centralised
      server for IP address assignment.

   o  Merging support: No special merging mechanisms are discussed in
      this solution.  Also, no in-service Non-unique Address Detection
      is used which makes the merging support not feasible.

   o  Prefix assignment support: the solution does not support the
      assignment of IPv6 prefixes to nodes.

   o  Protocol overhead: depends on the approach utilised.  If extended
      control messages of the MANET routing protocol -- including global
      prefix information -_ are used the solution introduces low
      overhead, but if gateway advertisement messages are periodically
      flooded (with the hop limit field set to an appropriate value in
      the MANET) then the solution introduces high overhead.

2.2.1.5.  Multihop Radio Access Network (MRAN) Protocol Specification
          (Hofmann)

   This proposed solution [24] presents the Multihop Radio Access
   Network (MRAN) protocol, which is an IPv6-based protocol for the
   interconnection of ad hoc networks and the Internet.  MRAN proposes
   an approach that enables mobile ad hoc nodes to communicate with
   correspondent nodes on the Internet.  The application scenario of
   this protocol is mainly when multiple gateways are available and
   mobile nodes are frequently changing these gateways.  The gateways
   are supposed to be fixed and advertising different prefixes.  MRAN
   treats the gateways discovery and selection, the autoconfiguration of
   global addresses, and the packet forwarding to/from the fixed
   network.

   Assumptions: It is assumed that mobile nodes (MNs) and Gateways (GWs)
   use local addresses for communication within the MANET and that
   routing is performed by a MANET routing protocol.  It is also assumed
   that a flooding protocol is used for broadcasting certain MRAN
   control messages, where the flooding functionality may be provided by
   the routing protocol.

   Approach description: The operation of MRAN involves several



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   functions: GW discovery, GW selection, address autoconfiguration,
   registration with the GW, packet forwarding and multi-hop handovers.
   Three modes of GW discovery are proposed and the choice between them
   depends on the application scenario.  In proactive GW discovery, all
   GWs periodically broadcast advertisement messages "GW_ADV", where MNs
   in proactive mode requiring Internet access waits until they receive
   such a message.  The reactive mode discovery allows MNs to discover
   the available GWs when needed through broadcasting a GW solicitation
   message.  A GW receiving such a message replies by unicast solicited
   GW advertisement message "sol_GW_ADV" to the MN.  Hybrid GW discovery
   mode is a combination of both proactive and reactive discovery, where
   the GW is in proactive mode and the MN is in reactive one.  All GW
   advertisement messages contain the GW globally valid prefix of 64
   bits length.  The GW selection process allows each MN to select the
   closet GW with respect to the number of hops.  Other additional
   metrics may be included in the selection process.  After the GW
   selection, the MN uses the selected GW's prefix and its own EUI-64 to
   autoconfigure the global address.  It may subsequently perform a Non-
   unique Address Detection.  Registration with the selected GW should
   take place, where the MN sends a registration request message
   "MN_REG" to the selected GW.  A GW receiving this message replies by
   a registration acknowledgement message "MN_REG_ACK" indicating the
   successful registration.  The MN then periodically repeats the
   registration process and the registration may be used for other
   purposes as well (for instance the AAA).  To assure appropriate
   packet forwarding between each MN and its selected GW, payload
   packets are tunnelled between MNs and GWs in both directions.  The
   tunnelling approach uses IP-in-IP encapsulation thus allowing using
   local addresses for intra-MANET communication.  In the tunnel from
   the GW to the MN, the destination address of the inner IP header is
   the MN global address and the destination address of the outer header
   is the local address of the MN.  On the other hand, in the tunnel
   from the MN to the GW, the destination address of the inner IP header
   is the CN global address, whereas the destination address of the
   outer header is the local address of the GW.  In the case of MN's
   disconnection from its current GW while communicating with a CN in
   the Internet, multihop handover takes place.  Thus, the MN has to
   discover, select and register with another GW.  This is called a
   "forced multihop handover".  For optimisation reasons, the MN may
   also select a new GW that could be more close than the current GW.
   In this case, the MN performs the registration with the new GW while
   it is connected to the current one.  This is known as "optimised
   multihop handover", and is much faster than the forced one.

   Maintenance takes place through creating two tables: i) GW table, and
   ii) MN table.  MNs maintain a GW table storing information about the
   available GWs (local address, prefix, expiration time, registration
   expiration).  A table entry is created when the MN receives a GW_ADV



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   or Sol_GW_ADV messages.  On the other hand, GWs maintain MN tables
   storing information about mobile nodes having a valid registration,
   where each entry in this table stores the following information on
   MNs (local address, global address, registration expiration time).

   Based on [2], this solution has the following key features:

   o  MANET scenario: This proposed solution targets connected MANET
      scenarios enabling mobile nodes to communicate with correspondent
      nodes in the Internet.

   o  Routing protocols' dependency: This proposed solution works
      independent of the MANET routing protocol.

   o  Address uniqueness: The proposed solution may use a Non-unique
      Address Detection mechanism.

   o  Distributed/Centralised approach: The proposed solution uses a
      distributed approach, where it does not solicit any centralised
      server for IP address assignment.

   o  Merging support: No special merging mechanisms are discussed in
      this solution.  Also, no in-service Non-unique Address Detection
      is used which makes the merging support not feasible.

   o  Prefix assignment support: This proposed solution supports
      prefixes assignment, where the different gateways are responsible
      for IPv6 prefixes advertisements.

   o  Protocol overhead: the solution integrates several mechanisms and
      there is a number of flooding used to achieve the proper
      mechanisms' functioning.  The overhead in this solution mainly
      lies in the assumption of an existing flooding protocol for
      broadcasting certain MRAN control messages, and GWs periodical
      broadcast of GW_ADV messages (containing the GW prefix) when
      proactive GW discovery is applied.  Also, GW_Solicitation messages
      are broadcast on-demand when reactive GWs discovery is applied,
      and periodical MN_REG messages are sent to the selected GWs by
      each node requesting an IP address which is acknowledged by a
      MN_REG_ACK by the selected GW.  Furthermore, additional messages
      are used for maintenance.

2.2.1.6.  Automatic IP Address Configuration in VANETs (Fazio et al.)

   Automatic IP address configuration is a challenging and still
   unexplored issue in vehicular ad hoc networks (VANETs) environments,
   where the vehicles' high mobility and variant density impede the
   direct utilisation of traditional networking techniques and



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   protocols.  Aiming at integrating VANETs within the Internet and
   providing passengers with any kind of Internet applications, the IP
   address represents the natural identifier in the system.  This work
   [25] proposes an IP autoconfiguration solution in VANETs environment,
   exploiting the VANETs topology and an enhanced DHCP service with
   dynamically elected leaders to provide a fast and reliable IP address
   configuration.

   Assumptions: It is assumed that the network topology is linear and
   that a group of nodes move following a track with an internal
   mobility with respect to each other.  It is also assumed that the
   relative speed between nodes is low.

   Approach description: This work proposes a novel automatic IP address
   configuration protocol named Vehicular Address Autoconfiguration
   (VAC), that is characterised by a low configuration time.  VAC
   represents the first protocol for IP address configuration in VANETs.
   It exploits the VANET topology and a distributed dynamic host
   configuration protocol (DHCP) runs by dynamically elected leader
   vehicles to quickly provide unique identifiers and reduce the
   frequency of IP address re-configurations due to mobility.  VAC
   organises leaders in a connected chain such that every node (vehicle)
   lies in the communication range of at least one leader.  This
   hierarchical organisation allows limiting the signal overhead for the
   address management tasks.  Only leaders communicate with each others
   to maintain updated information on configured addresses in the
   network.  Leaders act as servers of a distributed DHCP protocol and
   normal nodes ask leaders for a valid IP address whenever they need to
   be configured.

   VAC guarantees unique IP addresses within a defined SCOPE around the
   leader, where the SCOPE of the leader A is the set of leaders whose
   distance from A is less or equal to SCOPE hops.  Considering the
   normal node Y that received the IPy address from A, IPy will be
   unique as long as Y moves within the SCOPE of A. If Y goes out of the
   SCOPE of A, in order to still ensure the address uniqueness, Y has to
   ask the new leader for another address.  Considering that the
   relative speed between the nodes is low, changes in the address
   configuration due to having left the own leader's SCOPE are not
   frequent.

   Based on [2], this solution has the following key features:

   o  MANET scenario: The proposed solution targets connected MANET
      scenarios, enabling mobile nodes (vehicles) to communicate with
      correspondent nodes on the Internet.





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   o  Routing protocols' dependency: Apparently VAC does not depend on a
      special routing protocol.  However no clear definition is given on
      how and what control messages are exchanged in order to configure
      each node requiring an IP address.

   o  Address uniqueness: The proposed solution does not employ any Non-
      unique Address Detection mechanisms, however it guarantees address
      uniqueness for each configured node.

   o  Distributed/Centralised approach: The proposed solution employs a
      partially distributed approach, where distributed DHCP run by some
      mobile nodes (vehicles)that are elected in a dynamic manner to
      assign IP addresses to the requesting nodes.

   o  Merging support: No special merging mechanisms are explained in
      this proposed solution, however it could support merging.  The
      SCOPE principle together with the distributed DHCP permit the
      nodes to join/leave different SCOPES while acquiring a new address
      from the SCOPE leader.

   o  Prefix assignment support: This proposed solution does not employ
      any IPv6 prefix assignment to nodes.

   o  Protocol overhead: the hierarchical organisation in this solution
      limits the signalling overhead and avoids flooding.  The overhead
      in this solution mainly concerns: the signalling messages for
      communication between leaders nodes, the request messages sent by
      mobile nodes requesting an IP address from their leaders (this
      takes place in a limited scope), and the reply messages from the
      leaders to the requesting mobile nodes for assigning IP addresses
      (this also takes place in a limited scope).  It is noticed that
      this solution does not use Non-unique Address Detection mechanisms
      due to the distributed DHCP functionality among leader nodes,
      which helps in limiting the signalling overhead.

2.2.2.  Merging support

2.2.2.1.  Address Autoconfiguration in Optimized Link State Routing
          Protocol (Adjih et al.)

   This proposed solution [26] is based on the concept of conflict
   detection.  Each node periodically sends its address and an
   identifier.  The node identifier is a sequence of bits, of fixed
   length (L), that is randomly generated.  An address conflict is
   detected when the identifier mismatches.  This proposed solution is
   suitable for OLSR routing protocol with a light increase of control
   message overhead, however, it might be used with any MANET protocol.
   Two issues are addressed in this solution, an IPv6 stateless



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   autoconfiguration mechanism and a mechanism promoting address
   uniqueness in the situation where different ad hoc networks merge.

   Assumptions: Two assumptions are mainly considered in this proposed
   solution.  Firstly, it is assumed that the identifier of each node is
   globally unique in the network.  Secondly, it is assumed that a MANET
   may be isolated.

   Approach description: In this proposed solution, a new mobile node
   joining the network is assigned an IP address then it carries out a
   conflict detection procedure through running a Non-unique Address
   Detection mechanism.  If another node is detected to have the same
   address, the new joining node selects a new address.  The address
   assignment process takes place as follows: i)consulting a neighbour
   node that should configure an address for the new node.  The
   neighbour node then selects an IP address and sends it to the new
   node.  This takes place by control messages exchange. ii) picking up
   a random address inside a given subnet with MANET_prefix either from
   a pool of allocated addresses or through a set of addresses
   advertised by each MANET node and are believed not used.  In case of
   address pool existence, this pool could be reserved by the IANA for
   local use only (i.e. not forwarded outside MANET).  In addition, in
   case of MANETs connected to the Internet, nodes acting as gateways
   diffuse IPv6 router advertisement messages.  In this case each
   address in the pool would be a global address that can be seen from
   the outside.

   The Non-unique Address Detection algorithm uses a single special
   control message to perform conflict detection.  Each node
   periodically diffuses to the entire network a special message called
   MAD (Multiple Address Declaration).  This message contains the node
   address and a unique identifier for the node.  Several mechanisms are
   proposed for MAD messages propagation.  When using OLSR, propagation
   of MAD messages mainly relies on the MPR flooding, where a number of
   MPR selection rules are explained, presenting different options.  If
   another routing protocol is used, default pure flooding is used for
   MAD messages propagation.  In case of IP conflict discovery, this is
   resolved by the node with the smaller identifier in each conflicting
   pair.  This node should change its IP, selecting a new IP at random
   (that is believed to be free) following the same approach of IP
   address assignment.

   When OLSR routing protocol is used, an additional proposed option is
   using Passive Duplicate Detection.  In this case, the topological
   information diffused by the OLSR routing protocol is sufficient to
   detect address conflict.  However, some MPR selection mechanisms are
   used to ensure that the control messages are properly propagated.




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   Based on [2], this solution has the following key features:

   o  MANET scenario: This proposed solution targets both standalone and
      connected MANETs scenarios.

   o  Routing protocols' dependency: This proposed solution depends on
      the underlying routing protocol.

   o  Address uniqueness: the proposed solution comprises a Non-unique
      Address Detection mechanism.  The notion of passive duplicate
      detection is also used, where the solution makes use of the
      routing protocol messages propagation to detect the address
      conflicts.

   o  Distributed/Centralised approach: The proposed solution uses a
      distributed approach in the sense of not communicating with a
      centralised DHCP server to acquire IP addresses.

   o  Merging support: This proposed solution has a merging support,
      since the conflict detection process is periodically carried out
      by mobile nodes.  Thus, this solution assures address uniqueness
      in case of ad hoc networks merge.

   o  Prefix assignment support: This solution does not support IPv6
      prefix assignment to nodes.

   o  Protocol overhead: the solution adds low protocol overhead, since
      this solution benefits from the OLSR routing protocol signalling
      and MPRs concept to verify the address conflicts.  The signalling
      in this solution is limited to a single control message (MAD
      message) to perform conflicts detection.  If passive duplicate
      detection option is applied with OLSR, the overhead is almost
      none, as the topological information diffused by OLSR is
      sufficient to detect address conflict.  However, if another
      routing protocol is used (which is an option), the MAD messages
      have to be flooded resulting in a 'medium' overhead since the
      flooding is limited to only one message in this case.

2.2.2.2.  Extended Support for Global Connectivity for IPv6 Mobile Ad
          Hoc Networks (Cha et al.)

   The solution described in [27] proposes a stateful global IP
   autoconfiguration for MANETs with the goal of providing enhanced
   Internet connectivity to mobile ad-hoc networks.  This stateful
   autoconfiguration is performed through the exchange of extended
   control messages of MANET routing protocols.  The protocol is devised
   as an extension to AODV, but the concept may be applicable to
   proactive routing protocols.



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   Assumptions: The solution assumes that each node has a
   local_IP_address configured.

   Approach description: The protocol basically consists in nodes
   requesting global addresses to a gateway, which assigns a non-used
   address to the requesting node.  When an ad hoc node needs a global
   IP address it sends an Internet-gateway solicitation message (GW_SOL
   message).  The Gateway uses an Internet-gateway advertisement(GW_ADV
   message)to assign the solicited global IP address to the ad hoc node.

   Given the event that an ad hoc node which has a Global IP address
   (e.g., G-A1) assigned by a gateway (e.g., GW1) cannot reach GW1
   anymore due to a partition in the MANET but this ad hoc node has
   Internet connectivity through a different gateway (e.g..  GW2), the
   ad hoc node gets another global IP address from GW2 (e.g., G-A2) and
   it performs a Locator Registration Procedure with GW1.  This locator
   registration procedure is similar to Binding Updates in Mobile IPv6.
   Using this procedure the ad hoc node registers G-A2 as CoA -- Care of
   Address in Mobile IPv6 terminology -- of G-A1, so that ongoing
   communications are kept.

   More details can be found in [27].

   Based on [2], this solution has the following key features:

   o  MANET scenario: the solution targets connected MANETs.

   o  Routing protocols' dependency: although the protocol is devised as
      an extension to AODV, it could be applicable to proactive routing
      protocols.

   o  Address uniqueness: since non-duplicate addresses are assigned to
      ad hoc nodes, the proposed solution is Non-unique Address
      Detection-free.

   o  Distributed/centralised approach: the solution makes use of
      centralised servers (gateways) in order to assign IP global
      addresses.

   o  Merging support: given that the proposed solution assigns global
      IP addresses avoiding duplicates, merging is supported.  On the
      other hand it supports partitions through the Locator Registration
      Procedure.

   o  Prefix assignment support: the solution does not support the
      assignment of IPv6 prefixes to nodes.





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   o  Protocol overhead: the solution adds certain protocol overhead,
      since the mechanism appends some fields to AODV routing protocol
      (RREQ message) to ask for a global IP address and gateway
      information, and the replay (GW-ADV message) is unicast to the
      originator MANET node.  The solution includes the possibility of
      gratuitous GW_ADV broadcast periodically.

2.2.2.3.  Gateway and Address Autoconfiguration for IPv6 Adhoc Networks
          (Jelger et al.)

   This proposed solution [22] allows nodes in an ad hoc network to
   proactively discover a gateway/prefix pair to be used in building an
   IPv6 global address and to maintain a default route towards the
   Internet.  The core element of this proposed solution is the concept
   of "Prefix Continuity".  With prefix continuity, any node A that
   selected a given prefix P has at least one neighbour with prefix P on
   its path to the selected gateway G, thus assuring that each node on
   the path between node A and the Gateway G uses the same prefix P.

   Assumptions: It is assumed that each node can find a Gateway to
   connect with and that each node can be assigned a global address
   through this gateway.  It is also assumed that one (or possibly more)
   nodes of the ad hoc network should provide connectivity to the
   Internet, thus acting as Gateways to other nodes.

   Approach description: In this proposed solution, each Gateway (GW)
   periodically sends a GW_INFO message notifying nodes in the ad hoc
   network about its existence as well as the prefix it uses.  Some
   information in the GW_INFO message allows nodes to select the more
   appropriate GW when more than one GW exist.  Other information
   contained in this message concerns: the GW global address, the length
   of the prefix part of the address, and the distance to the gateway as
   perceived by the node sending the message.  The node receiving the
   GW_INFO message forwards it to its 1-hop neighbourhood, where the
   forwarder node is considered as the upstream node for each node that
   receives the message.  Among the transmitted GW-Info messages, each
   mobile node selects (through a selection algorithm) only one
   neighbour as its upstream neighbour and receives the GW_INFO messages
   from this neighbour (i.e. consider this upstream as an intermediate
   node to the gateway), then it forwards the message.  A node must not
   forward a GW_INFO message sent by a node that is not its upstream
   neighbour.  The destination address of the IPv6 header of the packet
   containing the GW_INFO message must be FF02::1 (all nodes), while the
   source address of such a packet must be the link local address of the
   sender.  Thanks to the prefix continuity, the routing via the GW can
   be achieved without the need of an IPv6 routing header.  Each mobile
   node creates its IPv6 global address as follows: {Extended Unique
   Identifier (EUI) of the interface from which the GW_INFO message is



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   received + prefix contained in the message}.  No Non-unique Address
   Detection mechanism is needed in this approach, as there is a very
   little probability of address duplication when EUI is used.

   Based on [2], this solution has the following key features:

   o  MANET scenario: This proposed solution targets connected MANETs
      scenarios.

   o  Routing protocols' dependency: This proposed solution is
      independent (in terms of message semantics) of the underlying
      routing protocol.  Thus, it can be integrated in the operation of
      the routing protocol or it can run as standalone daemon.

   o  Address uniqueness: The proposed solution does not depend on a
      Non-unique Address Detection procedure or mechanism.

   o  Distributed/Centralised approach: The proposed solution is
      distributed in the sense of not employing any centralised DHCP
      server.

   o  Merging support: Although no Non-unique Address Detection
      mechanism is used, this proposed solution supports networking
      partitioning and merging as it is based on generating an IPv6
      address for each node based on the prefix advertisements.

   o  Prefix assignment support: This proposed solution is based on the
      prefix continuity and is thus supporting prefix assignment.  Each
      gateway advertises the IPv6 prefix that it uses.

   o  Protocol overhead: depends on the network size and the number of
      GWs.  The main signalling in this solution mainly concerns the
      GW_INFO messages that are periodically sent by each GW notifying
      its existence as well as its prefix.  Since no Non-unique Address
      Detection mechanism is needed in this solution, this helps in
      limiting the signalling and hence the overhead.

2.2.2.4.  MANET Autoconfiguration using DHCP (Templin et al.)

   This draft [28] specifies a Virtual Enterprise Traversal (VET)
   abstraction for autoconfiguration and operation of routers in
   enterprise networks.  Enterprise networks connect routers over
   various link types.  Since certain MANETs can be considered as a
   challenging example of an enterprise network, the mechanisms
   described in this document can be applied to provide MANETs with IP
   address autoconfiguration capabilities.  This document has evolved a
   lot from its previous versions (and companion documents, such as [29]
   and [30], in which the author started to define an architecture in



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   which MANET Routers were attached to an imaginary shared link (called
   "virtual ethernet") that connected all the MRs in the MANET.

   Assumptions: It is assumed the existence of Enterprise Border
   Gateways (EBRs), that are routers that connect the enterprise network
   to provider networks and can delegate addresses/prefixes to other
   EBRs within the enterprise.

   Approach description: Regarding the applicability of the document to
   MANETs, it defines the Virtual Enterprise Traversal (VET), which is
   an abstraction that uses IP-in-IP encapsulation to span a multi-link
   enterprise in a single (inner) IP hop.  VET interfaces are Non-
   Broadcast, Multiple Access interface used for VET, which encapsulate
   each inner IP packet in any mid-layer headers plus an outer IP header
   then forwards it on an underlying interface such that the TTL/Hop
   Limit in the inner header is not decremented as the packet traverses
   the enterprise network.  In this way, the VET interface presents an
   automatic tunneling abstraction that represents the enterprise as a
   single IP hop.

   In order to autoconfigure a VET interface, the interface is first
   initialized (a link-local address is configured on the interface),
   then border routers (Enterprise Border Gateways, EBGs) are
   discovered, and last, IPv6 SLAAC is run on top of the VET.  EBGs
   plays the role of access routers (i.e., send Router Advertisements),
   so standard IPv6 SLAAC mechanisms can be used to configure VET
   interfaces.  DHCPv6 prefix delegation can also be used to configure a
   VET interface.

   Based on [2], this solution has the following key features:

   o  MANET scenario: the solution targets connected MANETs.

   o  Routing protocols' dependency: the solution is routing protocol
      independent.

   o  Address uniqueness: the proposed solution reuses SLAAC and DHCP
      mechanisms, by providing an abstraction that represents the
      enterprise network as a single IP hop.

   o  Distributed/centralised approach: the solution makes use of border
      routers (EBRs) in a similar way that routers sending Router
      Advertisements are used by SLAAC, or DHCPv6 servers are used when
      DHCPv6 prefix delegation is used.

   o  Merging support: the solution does not support merging.  No
      mechanisms are proposed to deal with different defined
      partitioning/merging scenarios.



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   o  Prefix assignment support: the solution supports the assignment of
      IPv6 prefixes to nodes.

   o  Protocol overhead: it does not add much overhead compared with
      SLAAC and DHCPv6.  It adds some overhead in terms of tunneling
      headers due to the VET approach.













































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3.  Security Considerations

   Due to the open wireless environment of ad hoc networks, IP
   autoconfiguration mechanisms are susceptible to a number of attacks.
   The autoconfiguration problem statement draft [1] states some
   security issues that worth consideration.













































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4.  IANA Considerations

   This document has no actions for IANA.
















































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5.  Acknowledgements

   We would like to thank all the AUTOCONF ML people that provided
   comments to the previous version of the I-D.  We would also like to
   thank Kilian Weniger for his useful review of this draft, and Thomas
   Clausen for his review and support on the continuity of this draft in
   another shape.

   The work of Carlos J. Bernardos and Maria Calderon has been partially
   supported by the Spanish Government under the POSEIDON (TSI2006-
   12507-C03-01) project.

   The work of Carlos J. Bernardos and Maria Calderon has also been
   partially supported by the EU through the ICT FP7 European Project
   CARMEN (INFSO-ICT-214994).  Apart from this, the European Commission
   has no responsibility for the content of this Internet-Draft.  The
   information in this document is provided as is and no guarantee or
   warranty is given that the information is fit for any particular
   purpose.  The user thereof uses the information at its sole risk and
   liability.































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6.  References

6.1.  Normative References

   [1]   Baccelli, E., Mase, K., Ruffino, S., and S. Singh, "Address
         Autoconfiguration for MANET: Terminology and Problem
         Statement", draft-ietf-autoconf-statement-04 (work in
         progress), February 2008.

   [2]   Moustafa, H., Bernardos, C., and M. Calderon, "Evaluation
         Considerations for IP Autoconfiguration Mechanisms in MANETs",
         draft-bernardos-autoconf-evaluation-considerations-03 (work in
         progress), November 2008.

   [3]   Chakeres, I., Macker, J., and T. Clausen, "Mobile Ad hoc
         Network Architecture", draft-ietf-autoconf-manetarch-07 (work
         in progress), November 2007.

6.2.  Informative References

   [4]   Perkins, C., "IP Address Autoconfiguration for Ad Hoc
         Networks", draft-perkins-manet-autoconf-01 (work in progress),
         November 2001.

   [5]   Weniger, K. and M. Zitterbart, "IPv6 Autoconfiguration in Large
         Scale Mobile Ad-Hoc Networks", European Wireless 2002 , 2002.

   [6]   Jeong, J., "Ad Hoc IP Address Autoconfiguration",
         draft-jeong-adhoc-ip-addr-autoconf-06 (work in progress),
         January 2006.

   [7]   Jeong, J., "Ad Hoc IP Address Autoconfiguration for AODV",
         draft-jeong-manet-aodv-addr-autoconf-01 (work in progress),
         July 2004.

   [8]   Vaidya, N., "Weak Duplicate Address Detection in Mobile Ad Hoc
         Networks", MOBIHOC'02 , 2002.

   [9]   Mohsin, M. and R. Prakash, "IP Address Assignment in a Mobile
         Ad Hoc Network", MILCOM 2002 , 2002.

   [10]  Tayal, A. and L. Patnaik, "An address assignment for the
         automatic configuration of mobile ad hoc networks", Personal
         Ubiquitous Computing , 2004.

   [11]  Mase, K. and C. Adjih, "No Overhead Autoconfiguration OLSR",
         draft-mase-manet-autoconf-noaolsr-01 (work in progress),
         April 2006.



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   [12]  Weniger, K., "Passive Duplicate Address Detection in Mobile Ad
         hoc Networks", IEEE Wireless Communications and Networking
         Conference (WCNC) , 2003.

   [13]  Weniger, K., "PACMAN: Passive autoconfiguration for mobile ad
         hoc networks", IEEE Journal on Selected Areas in
         Communications, vol. 23, no. 3, Mar 2005  pp. 507-519 , 2005.

   [14]  Mase, K. and K. Weniger, "PDAD-OLSR: Passive Duplicate Address
         Detection for OLSR", draft-weniger-autoconf-pdad-olsr-01 (work
         in progress), June 2006.

   [15]  Baccelli, E., "OLSR Passive Duplicate Address Detection",
         draft-clausen-olsr-passive-dad-00 (work in progress),
         July 2005.

   [16]  Jeong, H., "Passive Duplicate Address Detection for On-demand
         Routing Protocols", draft-jeong-autoconf-pdad-on-demand-01
         (work in progress), April 2007.

   [17]  Zhou, H., Ni, L., and M. Mutka, "Prophet Address Allocation for
         Large Scale MANETs", Proceedings of INFOCOM 2003 , 2003.

   [18]  Ruffino, S. and P. Stupar, "Automatic configuration of IPv6
         addresses for MANET with multiple gateways  (AMG)",
         draft-ruffino-manet-autoconf-multigw-03 (work in progress),
         June 2006.

   [19]  Clausen, T. and E. Baccelli, "Simple MANET Address
         Autoconfiguration", draft-clausen-manet-address-autoconf-00
         (work in progress), February 2005.

   [20]  Ruiz, P. and F. Ros, "Extensible MANET Auto-configuration
         Protocol (EMAP)", draft-ros-autoconf-emap-02 (work in
         progress), March 2006.

   [21]  Wakikawa, R., "Global connectivity for IPv6 Mobile Ad Hoc
         Networks", draft-wakikawa-manet-globalv6-05 (work in progress),
         March 2006.

   [22]  Jelger, C., "Gateway and address autoconfiguration for IPv6
         adhoc networks", draft-jelger-manet-gateway-autoconf-v6-02
         (work in progress), April 2004.

   [23]  Suan, Y., Belding-Royer, E., and C. Perkins, "Internet
         Connectivity for Ad hoc Mobile Networks", International Journal
         of Wireless Information Networks special issue on 'Mobile Ad
         Hoc Networks (MANETs): Standards, Research, Applications' ,



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         2002.

   [24]  Hofmann, P., "Multihop Radio Access Network (MRAN) Protocol
         Specification", draft-hofmann-autoconf-mran-00 (work in
         progress), March 2006.

   [25]  Fazio, F., Palazzi, C., Das, S., and M. Gerla, "Automatic IP
         Address Configuration in VANETs", ACM VANET 2006 Workshop co-
         located with Mobicom 2006 , 2006.

   [26]  Laouiti, A., "Address autoconfiguration in Optimized Link State
         Routing Protocol", draft-laouiti-manet-olsr-address-autoconf-01
         (work in progress), July 2005.

   [27]  Cha, H., Park, J., and H. Kim, "Extended Support for Global
         Connectivity for IPv6 Mobile Ad Hoc Networks",
         draft-cha-manet-extended-support-globalv6-00 (work in
         progress), October 2003.

   [28]  Templin, F., "Virtual Enterprise Traversal (VET)",
         draft-templin-autoconf-dhcp-20 (work in progress),
         October 2008.

   [29]  Templin, F., "MANET Autoconfiguration over Multilink Sites",
         draft-templin-autoconf-multilink-00 (work in progress),
         February 2007.

   [30]  Templin, F., "MANET Autoconfiguration over Virtual Ethernets",
         draft-templin-autoconf-virtual-00 (work in progress),
         February 2007.





















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Appendix A.  Change Log

   Changes from -03 to -04:

   o  New release to keep the document alive.

   o  Update of some references and the associated solution description.

   Changes from -02 to -03:

   o  New release to keep the document alive.

   o  Update of some references.

   Changes from -01 to -02:

   o  The classification criteria section has been removed, since it is
      now part of the evaluation considerations in [2].  Solutions are
      now analysed conforming to some of these evaluation considerations
      in [2].

   o  The Conclusions section has been removed.

   o  The Terminology section has been removed.

   o  The term "DAD" has been removed in the document (when possible),
      using Non-unique Address Detection instead.

   o  Many editorial changes.

   Changes from -00 to -01:

   o  The structure of the I-D has modified, classifying the analysed
      solutions according to a number of useful criteria, conforming to
      the AUTOCONF problem statement draft and the MANET architecture
      draft.

   o  More solutions have been added to the I-D.

   o  Adding of a security consideration section.











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Authors' Addresses

   Carlos J. Bernardos
   Universidad Carlos III de Madrid
   Av. Universidad, 30
   Leganes, Madrid  28911
   Spain

   Phone: +34 91624 6236
   Email: cjbc@it.uc3m.es


   Maria Calderon
   Universidad Carlos III de Madrid
   Av. Universidad, 30
   Leganes, Madrid  28911
   Spain

   Phone: +34 91624 8780
   Email: maria@it.uc3m.es


   Hassnaa Moustafa
   France Telecom
   38-40 rue du General Leclerc
   Issy Les Moulineaux  92794 Cedex 9
   France

   Phone: +33 145296389
   Email: hassnaa.moustafa@orange-ftgroup.com





















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Full Copyright Statement

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