MANET Autoconfiguration (AUTOCONF) S. Singh
Internet-Draft J. Kim
Expires: September 7, 2006 Samsung AIT, Comm Lab
C. Perkins
Nokia Research Center,
Communications Systems Laboratory
T. Clausen
LIX, Ecole Polytechnique
P. Ruiz
University of Murcia
March 6, 2006
Address autoconfiguration for MANETs: definition and problem statement
draft-singh-autoconf-adp-03
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Abstract
A Mobile Ad Hoc NETwork (MANET) is formed by the association of
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mobile devices, usually wireless and capable of multi-hop
communication among themselves even if there is no networking
infrastructure available. MANET properties such as multi-hop,
autonomous, etc requires separate address autoconfiguration
mechanism. This document provides definition, problem statement and
goals for ad hoc networks address autoconfiguration.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Problem statement . . . . . . . . . . . . . . . . . . . . . . 7
4.1. Stand-alone ad hoc network . . . . . . . . . . . . . . . . 7
4.2. Ad hoc network at the edge of infra-structure network . . 8
4.3. Temporarily hybrid ad hoc network . . . . . . . . . . . . 9
4.4. Network merger and partitioning . . . . . . . . . . . . . 9
5. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6. Security Considerations . . . . . . . . . . . . . . . . . . . 11
Appendix A. Normative References . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
Intellectual Property and Copyright Statements . . . . . . . . . . 15
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1. Introduction
A Mobile Ad Hoc NETwork (MANET) is formed by the association of
mobile devices, usually wireless and capable of multi-hop
communication among themselves even if there is no networking
infrastructure available. However, it is generally expected that, if
some MANET nodes are connected to external IP networks (e.g.
Internet), they might act as gateways towards those networks.
Several independent solutions have been proposed on interconnecting
MANETs and the Internet[4][5][7]. Most of the solutions are related
to the issues of discovering Internet gateways and auto- configuring
global IP addresses that are routable within the Internet. Usually,
autoconfiguration of IP addresses in MANET is also required even when
the MANET is isolated from external networks.
Currently there is no standard definition for commonly used MANET
autoconfiguration related terminologies such as MANET local address,
standalone MANET, etc. This document provides definition of such
terminologies and states problems and goals for ad hoc network IP
address autoconfiguration. At places, address configuration as used
in this document may be read as prefix configuration.
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2. Terminology
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC2119 [5].
Mobile Ad hoc Network (MANET) - An ad hoc network formed autonomously
in an arbitrary manner by the association of mobile devices,
usually wireless and capable of multi-hop communication among
themselves. MANETs are characterized by highly dynamic
topologies; that is, network links come and go quickly in
comparison to existing wired networks. The dynamic topology may
be a consequence of wireless link environment effects and/or node
mobility.
MANET Node - A device with one or more wireless interfaces and
associated IP address(es) which is used by the MANET routing
protocol in use.
MANET local address - An IP address configured on a MANET node and
valid for communication among MANET nodes that are part of the
same ad hoc network. Nodes MUST NOT communicate with other nodes
outside the MANET using this address.
Global address - An IP address configured on a MANET node and valid
for communication with nodes in the Internet, as well as
internally within the MANET.
Internet gateway - An edge node connected to MANET as well as to the
Internet and capable of providing bidirectional connectivity
between the Internet and MANET . These gateways are expected to
provide topologically correct IPv6 prefixes. Internet gateways
mostly run ad hoc routing protocols as well as infrastructure
network protocols such as OSPF.
Duplicate Address Detection (DAD) - The process by which a node
confirms the uniqueness of an address it wishes to configure or
has already configured. A node already equipped with an IP
address participates in DAD in order to protect its IP address
from being used by another node.
Standalone ad hoc network - An independent ad hoc network which has
no connectivity, either direct of via Internet gateways, to any
other IP networks such as the Internet.
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Hybrid ad hoc network - An ad hoc network which has connectivity,
either direct of via Internet gateways, to other IP networks such
as the Internet. They can be envisioned as a standalone MANET
with one or more Internet Gateways taking part in both MANET and
the Internet.
Network merger - The process by which two or more ad hoc networks
(either standalone or hybrid), previously disjoint, get connected.
In general, network merger happens as a consequence of node
mobility and/or wireless link environment.
Network partitioning - The process by which an ad hoc network (either
standalone or hybrid) splits into two or more disconnected ad hoc
networks. In general, this proccess happens as a consequence of
node mobility and/or wireless link environment.
Network merger detection - The process by which MANET nodes detect
network merger.
Network partition detection - The process by which MANET nodes detect
network partition.
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3. Requirements
o Network routes (those valid for an entire network prefix instead
of just a single node) require reachability to every node which
exists within the prefix, just as within the Internet.
o An Internet gateway can be treated as a default router for the
Internet.
o An Internet gateway SHOULD maintain active routes for all nodes
within the MANET which are actively engaged in communications with
their partners in the Internet.
o Control signals meant for nodes in the ad hoc network MUST NOT
leak into the Internet.
o Nodes within the Internet cannot distinguish whether or not a
gateway offers connectivity to an ad hoc network or some other
sort of stub network.
o If two gateways advertise connectivity to the same prefix, then
those two gateways MUST coordinate their routing tables so that
they exhibit equal reachability for all nodes within that routing
prefix.
o Gateways may offer several different prefixes. A node may choose
which gateway and routing prefix to use for autoconfiguration
according to any convenient criterion; the methods for making the
determination are not constrained to be only those specified
within a MANET autoconfiguration protocol specification.
o Autoconfigured addresses are likely to have lifetimes associated
with them, and after the lifetime expires use of the address
should be immediately discontinued or negotiated.
o Address autoconfiguration solution SHOULD work well even when some
nodes are temporarily disconnected or asleep.
o When duplicate addresses are detected, those nodes with
conflicting addresses MUST resolve the conflict.
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4. Problem statement
Specifications have been developed for address autoconfiguration in
the traditional IP based network such as RFC 2462, RFC 3315 and RFC
2461. However, these specifications are not applicable to MANET
nodes as-is due to their unique properties. Unlike in the
traditional IP networks, each MANET node besides being traffic end-
point, normally expected to forward traffic destined for other hosts.
That is each MANET node normally acts as a "router" as well as a
"host". Additionally, the notion of all nodes being able to access a
shared communication medium fails in MANET since every node in a
particular MANET do not share the same physical link. In MANET, a
single transmission does not suffice for a broadcast or link-local
multicast to reach all nodes constituting a particular MANET.
Transmissions which are otherwise not supposed to be forwarded by
routers, such as limited broadcast and link-local multicast, may need
to be forwarded by the intermediate nodes in order to reach desired
MANET node. In other words, nodes constituting a MANET do not share
access to a single multicast-capable link for signaling. The above
mentioned RFCs for address autoconfiguration in the traditional IP
network assume that subnet-local signals (e.g. link-local multicast
signals) are received by each of the hosts on the particular subnet
without being forwarded by the routers defining the subnet boundary.
Ad hoc networks can either be deployed as a standalone network or as
an edge network attached to the Internet. Indeed, IETF MANET WG has
this point of view for developing the MANET routing protocols.
There is a growing requirement for a standard address
autoconfiguration solution for MANETs that can be used by MANET nodes
constituting standalone networks or edge networks. The solution
should be designed with minimum modification, if any, and should be
compliant with the specifications that are widely used in the
traditional IP networks. The address autoconfiguration protocol has
to carefully distinguish between cases when a gateway offers a
routing prefix, from the case when a "local" prefix has to be used
since no routing prefix is available for the purpose.
4.1. Stand-alone ad hoc network
Standalone ad hoc networks are formed by a group of MANET nodes
capable of spontaneously forming a multi-hop ad hoc network and has
no connection (either direct of via gateways) to other IP networks
such as the Internet.
Examples of standalone ad hoc networks are temporary networks such as
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conference-room networks, battlefield networks, surveillance
networks, etc. In order to communicate among themselves, MANET nodes
need to use Standard IP address autoconfiguration mechanism for
configuring their interface(s). These addresses should be routable
only within the particular ad hoc network and their uniqueness should
be maintained even in situations where two or more networks,
initially disjoint, merge together to form a single network. Due to
the mobility and wireless properties of the nodes, network merger can
occur anytime.
4.2. Ad hoc network at the edge of infra-structure network
H1
|
+---------------+
| Internet |
+---------------+
* *
* *
GW1* *
| GW2
| |
---N1 |
/ | |
N4 | N2--- N5
| |
N3-----------+
Fig. 1: Hybrid ad hoc network connected to Internet.
Hybrid networks can be envisioned as an standalone network connected
to the Internet via one or more Internet Gateways. These gateways
are located between the two networks and are capable of providing
globally routable addresses as well as bi-directional connectivity to
the ad hoc nodes connected to them either directly (1-hop) or via one
or more intermediate nodes. These gateways may either be fixed or
mobile, single or multiple, equipped with one or more wired and/or
wireless interfaces.
Fig.1. shows an ad hoc network deployed at the edge of the Internet.
Ad hoc nodes may use Internet gateway for global prefix allocation
and globally routable address configuration. However, for such
network sufficient but limited detail about Internet gateway(s)
operation is required.
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4.3. Temporarily hybrid ad hoc network
Temporarily hybrid MANET scenario arises due to the situation where
an ad hoc network may be sometimes stand-alone and sometimes
connected to the Internet e.g. a car or subway network connected
while parked or at station and disconnected otherwise.
Problems related with this ad hoc network operation scenario are
similar to those introduced in the above two scenarios. However, in
this case, ad hoc nodes should detect the loss of reachability to the
Internet and SHOULD maintain their allocated addresses for the
lifetime which has been assigned during the autoconfiguration
process. For local addresses, no such lifetime is necessary, but
could anyway be assigned as a minimal protection against
partitioning.
4.4. Network merger and partitioning
By the nature of MANET, two or more ad hoc networks which are
initially isolated, can merge together or a single ad hoc network can
get partitioned into two or more separate networks, at any moment in
time. As a consequence of network partitioning, some of the routes
in MANET nodes become invalid and hence some nodes may become
unreachable. It is desirable that network partitioning is detected
due to reasons such as re-use of resources that were initially used
by the outgoing nodes.
Network merger can lead to duplication of addresses. Normally, once
an address is allocated to a node, it continues using it and
collaborating to detect and resolve duplicates in case its address is
allocated to any other node. Since initially isolated networks had
allocated addresses independent with each other, there remains some
probability of more than one node using same address. Worst possible
scenario can occur when number of address conflicts after merger are
as many as number of nodes. This can happen if, for example,
addresses were allocated within initially independent MANETs from the
same address-range.
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5. Goals
Goals listed below are by no means exhaustive. Additional goals may
be found necessary as the protocol design, implementation and
deployment takes place. Below listed goals is an effort to give a
bigger scope and as such may or may not fall within the scope of the
AUTOCONF WG. These goals include:
- As mentioned in the above sections, MANETs can be either
standalone or connected to the Internet via one or more Internet
gateways. MANET nodes MUST implement a mechanism to configure
"local address(es)" when standalone. It MAY configure global
address(es) when connected to the Internet. Nodes MUST ensure
address uniqueness, explained under next bullet, before
configuring them to their interfaces. It MAY be required that the
configured global addresses are usable even after connectivity
with the Internet is lost.
- Each node MUST collaborate and resolve conflicts in case its
address is duplicated to ensure uniqueness of the tentative
address. If the particular address is being used by some other
node, either one or both nodes MUST stop using the address. In
this situation an alternative address MAY be generated.
- As mentioned in section 4.4, network Merger is quite possible in
MANETs. This may or may not result in multiple nodes using same
address. However, it is desirable that each node runs mechanism
to ensure the uniqueness of its current address-in-use.
- Network partitioning is equally probably scenario in MANET and,
is desirable that network partitioning is detected due to the
reasons mentioned in section 4.4. Hence, MANET nodes MAY need a
mechanism, either independent or integrated with the the main
protocol, to detect network partitioning.
- Protocol should be designed to avoid as many security pitfalls
as can be avoided. This may involve using collaboration histories
and out-of-band mechanisms requiring user interventions.
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6. Security Considerations
Since this document does not specify any protocol, no additional
security vulnerabilities are created. However, given the importance
of an aoutoconfiguration protocol as a bootstrapping process, it is
important that protocols are designed trying to provide as much
security as possible. Previous work on security in stand-alone ad
hoc networks has shown that only a limited amount of security can be
provided due to the absence of central entities or security
infraestructures capable of validating the identity of nodes. In
particular, given that the main goal of an autoconfiguration protocol
is to provide nodes with IP addresses, special care needs to be taken
to study the mapping of identities to addresses. In particular, this
is of paramount importance in MANETs, in which reconfigurations and
duplicates may occur. In the case of hybrid MANET scenarios,
security remains being a difficult challenge, but an additional
number of security services are likely to be provided including among
others authentication and access control. Security mechanisms for
autoconfiguration protocols SHOULD be designed so that they continue
being effective even when parts of the network get temporarilly
partition, and eventually lose Internet connectivity.
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7. Acknowledgements
The authors would like to acknowledge the following people
for their technical contributions, discussions, reviews and
comments : Ruffino Simone, Raquel Morera, Jari Arkko, Dave Thaler,
Joe Macker, Christophe jelger, Alicia Trivino and Carlos J. Bernardos.
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Appendix A. Normative References
o [1] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
o [2] Thomson, S. and T. Narten, "IPv6 Stateless Address
Autoconfiguration", RFC 2462, December 1998.
o [3] Engelstad, P., Tonnesen, A., Hafslund, A. and G. Egeland,
"Internet Connectivity for Multi-Homed Proactive Ad Hoc Networks",
First IEEE International Conference on Sensor and Ad hoc
Communications and Networks, October 2004.
o [4] Ryuji Wakikawa et. al. Global connectivity for IPv6 Mobile Ad
Hoc Networks, IETF "draft-wakikawa-manet-globalv6-03.txt"
o [5] Shubhranshu Singh, Kim, JH., Choi, YG., Kang, KL. and YS.
Roh, "Mobile multi-gateway support for IPv6 mobile ad hoc
networks" I-D draft-singh-manet-mmg-00.txt, June 2004.
o [6] Perkins, C., Malinen, J., Wakikawa, R. and E. Belding-Royer,
"IP Address Autoconfiguration for Ad Hoc Networks", I-D
draft-perkins-manet-autoconf-01.txt, November 2001.
o [7] Cha, H., Park, J. and H. Kim, "Extended Support for Global
Connectivity for IPv6 Mobile Ad Hoc Networks", October 2003.
o [8] Jeong, J., Park, J., Kim, H. and D. Kim, "Ad Hoc IP Address
Autoconfiguration", I-D draft-jeong-adhoc-ip-addr-autoconf-02.txt,
February 2004.
o [9] Paakkonen, P., Rantonen, M. and J. Latvakoski, "IPv6
addressing in a heterogeneous MANET-network", I-D
draft-paakkonen-addressing-htr-manet-00.txt, December 2003.
o [10] Jelger, C., Noel, T. and A. Frey, "Gateway and address
autoconfiguration for IPv6 adhoc networks", I-D
draft-jelger-manet-gateway-autoconf-v6-02.txt, April 2004.
o [11] Sun, Y. and E. Belding-Royer, "A study of dynamic addressing
techniques in mobile ad hod networks", I-D Wireless communication
and mobile computing, May 2004.
o [12] C. Bernardos and M. Calderon, "Survey of IP address
autoconfigura- tion mechnisms ofr MANETs," Internet Draft,
draft-bernardos-manet- autoconf-survey-00.txt, July 2005, work in
progress.
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o [13] Engelstad, P., Tonnesen, A., Hafslund, A. and G. Egeland,
"Internet Connectivity for Multi-Homed Proactive Ad Hoc Networks",
First IEEE International Conference on Sensor and Ad hoc
Communications and Networks, October 2004.
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Authors' Addresses
Shubhranshu
Samsung AIT, Comm Lab
Phone: +82 31 280 9569
Email: Shubranshu@gmail.com
JaeHoon Kim
Samsung AIT, Comm Lab
Phone: +82 31 280 9532
Email: jaehoonk@samsung.com
Charles E. Perkins
Nokia Research Center, Communications Systems Laboratory
Phone: +1 650 625 2986
Email: charliep@iprg.nokia.com
Thomas Heide Clausen
LIX, Ecole Polytechnique
Phone: +33 6 6058 9349
Email: T.Clausen@computer.org
URI: http://www.lix.polytechnique.fr/Labo/Thomas.Clausen/
Pedro M. Ruiz
University of Murcia
Phone: +34 968367646
Email: pedrom@dif.um.es
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