IETF AUTOCONF Shubhranshu. Singh
Internet-Draft JaeHoon. Kim
Expires: August 18, 2005 SAMSUNG AIT
Charles E. Perkins
Nokia Research Center
Pedro M. Ruiz
University of Murcia
Thomas. Clausen
Ecole polytechnique
February 14, 2005
Ad hoc network autoconfiguration: definition and problem statement
draft-singh-autoconf-adp-00.txt
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Abstract
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A Mobile Ad hoc Network (MANET) is formed by the association of
wireless and mobile devices capable of communicating among themselves
even if there is no networking infrastructure available. The
autonomous nature of these networks, requires the existence of an
autoconfiguration mechanism. This document provides definition,
problem statement and solution guidelines for ad hoc network
autoconfiguration.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Assumption . . . . . . . . . . . . . . . . . . . . . . . . . 7
4. Problem statement . . . . . . . . . . . . . . . . . . . . . . 8
4.1 Stand-alone ad hoc network . . . . . . . . . . . . . . . . 8
4.2 Ad hoc network at the edge of infra-structure network . . 8
4.3 Temporarily hybrid ad hoc network . . . . . . . . . . . . 9
4.4 Dealing with network merges and partitions . . . . . . . . 10
5. Autoconfiguration solution guidelines . . . . . . . . . . . . 11
6. Security Considerations . . . . . . . . . . . . . . . . . . . 12
7. Normative References . . . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 12
Intellectual Property and Copyright Statements . . . . . . . . 14
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1. Introduction
A Mobile Ad hoc Network (MANET) is formed by the association of
wireless and mobile devices capable of communicating among themselves
even if there is no networking infrastructure avaiplable. However,
it is generally expected that, if some MANET nodes are connected to
external networks (e.g. Internet) some of them might act as gateways
towards those networks.
There are a number of solutions on interconnecting ad hoc networks to
Internet[4][5][7]. Most of the solutions are tightly related to
the issue of autoconfiguring global addresses routable in the
Internet, and discovering Internet gateways at the same time.
However, it is generally expected that autoconfiguration of addresses
in MANET is also required even when the MANET is isolated from
external networks.
Currently there is no standard definition for commonly used ad hoc
network autoconfiguration related terminologies such as manet local
prefix, manet local address, etc. This document provides definition
of such terminologies in addition to problem statement and solution
guidelines for ad hoc network autoconfiguration.
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2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", "OPTIONAL", and
"silently ignore" in this document are to be interpreted as described
in RFC 2119 [1].
Mobile Ad hoc Network (MANET)
- A network formed by a set of mobile devices equipped with one
or more wireless interfaces. Nodes are characterized by random
mobility and run ad hoc routing protocols for multi-hop
communication.
MANET Node
- A device with one or more wireless interfaces and associated
IPv4 or IPv6 address which is used by the MANET routing
protocol in use.
MANET local address
- An IPv4 or IPv6 address configured on a MANET node, which is
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.
Manet local prefix
- Predefined network prefix used by manet nodes to generate
address for communication within the multi-hop environment.
Global address
- An IPv4 or IPv6 address configured on a MANET node, which is
valid for communication with the nodes located in the Internet.
These addresses can also be used for communication with nodes
within the MANET.
Internet gateway
- A node connected to ad hoc network as well as to the Internet
and capable of providing global addressing and bidirectional
connectivity to MANET nodes. Internet gateways should provide
topologically correct IPv6 prefixes. This process can be done
in a reactive, proactive or hybrid manner. Internet gateway
mostly runs ad hoc routing protocols as well as infrastructure
network protocols such as OSPF.
Interface identifier
- An unique number associated to each interface of a MANET node,
that can be used for the generation of a global address from a
network prefix.
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Duplicate Address Detection (DAD)
- The process by which a node confirms the uniqueness of an
address it has already configured or wishes to configure. 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
- A network consisting of a group of MANET nodes capable of
spontaneously creating a multi-hop ad hoc network without any
connection (either direct of via gateways) to other IP networks
such as the Internet.
Hybrid ad hoc network
- A network formed by a group of MANET nodes, capable of
spontaneously forming a multi-hop ad hoc network, in which one
or more of the nodes act as Internet Gateways providing access
to other IP networks. They can be envisioned as a standalone
MANET with one or more Internet Gateways taking part both in
the MANET and in the external network. MANET nodes are able to
get global addressing as well as bidirectional connectivity
between these two networks.
Internet Gateway discovery
- The proccess by which a MANET node selects the Internet Gateway
through which it can communicate with a destination located in
the Internet. This process can be either integrated into ad
hoc routing protocols, integrated into autoconf messages or
introduced into an independent module.
Internet Gateway selection
- The process by which MANET nodes select the Internet gateway to
be used to communicate a MANET node with a destination located
in the Internet. This process is only required in hybrid ad
hoc networks. Different metrics can be used to make that
decission e.g. hop count, delay, node's processing
capabilities, power, etc.
Network merger
- The process by which two or more ad hoc networks (either
standalone or hybrid), previously disjoint, get connected. In
general, this proccess happens as a consequence of the mobility
of the nodes. When this happens, the autoconf process should
be able to re-establish the uniqueness of manet-local and
global addresses.
Network partitioning
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- The process by which an ad hoc network (either standalone or
hybrid) which was previously connected, gets split into two or
more disconnected ad hoc networks. In general, this proccess
happens as a consequence of the mobility of the nodes. When
this happens, some of the routes in MANET nodes become invalid
hence some nodes may become unreachable. Autoconfiguration
mechanisms should take into account these situations, and be
able to tolerate those partitions.
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3. Assumption
- Routes between nodes in the ad hoc network MUST NOT leak into the
Internet.
- 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.
- A gateway can be treated as a default router for the Internet.
- A gateway SHOULD maintain active routes for all nodes within the
MANET which are actively engaged in communications with their
partners in the Internet.
- 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.
- If two gateways advertise connectivity to the same routing prefix,
then those two gateways MUST coordinate their routing tables so
that they exhibit equal reachability for all nodes within that
routing prefix.
- Multiple gateways may offer several different routing prefixes. A
node may choose which gateway's 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.
- Autoconfigured addresses are likely to have lifetimes associated
with them, and after the lifetime expires use of the address
should be immediately discontinued.
- When duplicate addresses are detected, the node which has had the
address for the least amount of time MUST discontinue.
Alternatively, BOTH nodes MUST discontinue using this address.
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4. Problem statement
While there are several autoconfiguration specifications for IP-based
infrastructured networks such as RFCs 2461, 2462, 3315, etc,
currently there is no standard specification describing how ad hoc
nodes can auto-configure their IP addresses. Due to unique
characteristics of ad hoc networks such as multi-hop packet
forwarding, lack of any infrastructure e.g. DHCP server, random
mobility, etc, the specifications used by infrastructured network
cannot be directly used for ad hoc node autoconfiguration.
The main goal of the MANET autoconf is to develop solutions
for IPv4 and IPv6 address auto-configuration that are either
manet-local scope i.e. valid only within a particular ad hoc network
or global scope i.e. addresses that are routable on the global
Internet.
The autoconfiguration protocol has to carefully distinguish between
cases when a gateway offers a routing prefix, from the case when a
"manet local" prefix has to be used since no routing prefix is
available for the purpose. In this way, a single addressing solution
is obtained, but just as within the Internet there are different
kinds of addresses. Some parallels can be drawn between the "manet
local" addressing and the "zeroconf" solution devised within the IETF
working group of the same name. However, there may be differences
which are discovered as more development occurs towards the
specification of the address autoconfiguration protocol.
4.1 Stand-alone ad hoc network
Such ad hoc networks are not connected to any external network and
are self-sufficient in themselves. Such networks include conference
networks, battlefield, surveillance, etc.
For such MANETs, IPv4 and IPv6 address auto-configuration mechanism,
duplicate address detection and resolution mechanisms will be
developed considering the situation where nodes may be added or
removed randomly. Any address autoconfiguration mechanism for such
networks should take care of the lack of any pre-established and
reliable address or prefix allocation agency.
4.2 Ad hoc network at the edge of infra-structure network
Such network is shown in Fig.1.
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H1
|
+---------------+
| Internet |
+---------------+
* *
* *
GW1* *
| GW2
| |
---N1 |
/ | |
N4 | N2--- N5
| |
N3-----------+
Fig. 1: Hybrid ad hoc network connected to Internet.
Hybrid networks can be envisioned as stand-alone networks connected
to the Internet via one or more Internet Gateways. These gateways
are located between the two networks. Internet gateways may be
either fixed or mobile, single or multiple, equipped with wired
and/or wireless interfaces and should be able to provide global
addressing as well as bidirectional connectivity to the MANET nodes
connected to it either directly (1-hop) or through one or more
intermediate nodes.
MANET nodes may use Internet gateways for prefix allocation. This
may make the address configuration process comparatively simpler but
it introduces other issues such as how MANET nodes receive or
Internet gateways provide topologically correct routing prefixes.
Hence, for such network sufficient but limited detail about Internet
gateway discovery and operation will be provided, along with an
address autoconfiguration solution.
4.3 Temporarily hybrid ad hoc network
The third scenario considers the case in which an ad hoc network may
be stand-alone for most of the time but temporarily connected to the
infrastructured network (e.g. a car network connected while parked
and disconnected otherwise).
In this case, the nodes in the ad hoc network SHOULD maintain their
allocated addresses for the lifetime which has been assigned during
the autoconfiguration process. For manet-local addresses, no such
lifetime is necessary, but could anyway be assigned as the most
minimal protection against partitioning.
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4.4 Dealing with network merges and partitions
Two or more ad hoc networks may join together or a single ad hoc
network may get partitioned into two or more separate networks, at
any moment in time. While network partitioning may not cause any
severe problem in the MANET's operation, network merges may create
some issues related to the possibility of introducing more than one
node with the same address within the same MANET. Hence, appropriate
mechanism should be provided in order to ensure uniqueness of the
addresses configured by MANET nodes after a network merge.
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5. Autoconfiguration solution guidelines
In order to offer a lightweight but interoperable auto-configuration
mechanism a number of requirements SHOULD be satisfied. These
requirements include:
Extensibility
- The mechanism SHOULD be able to accomodate future extensions
and optimizations.
Efficiency
- Given that network resources tend to be scarce in MANETs,
autoconfiguration mechanisms SHOULD be lightweight in nature,
and avoid making an excessive use of the network resources.
Independence from ad hoc routing protocols
- Autoconfiguration mechanisms SHOULD be able to operate with
different proactive and reactive routing protocols.
Interoperable with fixed IP networks
- When there are one or more Internet gateways within a MANET,
the address autoconfiguration approach should provide global
addresses to MANET nodes in such a way that they MUST be able
to interoperate with any IP host in the Internet, using
standard protocols.
Resilience and robustness
- Given the dynamic nature of MANETs, autoconfiguration
mechanisms SHOULD be resilient and roubust to packet losses,
network partitions, network merges as well as disconnections
from fixed IP networks or Internet Gateways.
Validity both for IPv4 and IPv6
- Autoconfiguration mechanisms SHOULD be capable of working both
for IPV4 and IPv6 autoconfiguration.
Scalable
- MANET autoconfiguration protocols should avoid increasing
congestion in the MANET as the number of MANET nodes increases,
or as they travel at higher speeds, or as more communication
partners launch applications within the ad hoc network, or as
the frequency of network partitions increases.
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6. Security Considerations
Since this document does not specify any protocol, no additional
security vulnerabilities are created. However, experience with other
address autoconfiguration protocols indicates that it is difficult to
expect a very high degree of security. This is especially true in an
ad hoc network using manet-local addresses, since it may be
unfeasible to interact with any pre-existing security infrastructure.
Nevertheless, the protocols 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.
7. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Thomson, S. and T. Narten, "IPv6 Stateless Address
Autoconfiguration", RFC 2462, December 1998.
[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.
[4] Ryuji Wakikawa et. al. Global connectivity for IPv6 Mobile
Ad Hoc Networks, IETF "draft-wakikawa-manet-globalv6-03.txt"
[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.
[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.
[7] Cha, H., Park, J. and H. Kim, "Extended Support for Global
Connectivity for IPv6 Mobile Ad Hoc Networks", October 2003.
[8] Jeong, J., Park, J., Kim, H. and D. Kim, "Ad Hoc IP Address
Autoconfiguration",
I-D draft-jeong-adhoc-ip-addr-autoconf-02.txt, February 2004.
[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.
[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.
[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.
[12] 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.
Authors' Addresses
Shubhranshu Singh
SAMSUNG Advanced Institute of Technology
Comm & Network Lab
San 14-1, Nongseo-ri, Giheung-eup
Yongin-si, Gyeonggi-do 449-712
KOREA
Phone: +82 31 280 9569
Email: shubranshu@gmail.com
JaeHoon Kim
SAMSUNG Advanced Institute of Technology
Comm & Network Lab
San 14-1, Nongseo-ri, Giheung-eup
Yongin-si, Gyeonggi-do 449-712
KOREA
Phone: +82 31 280 9532
Email: jaehoonk@samsung.com
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Charles E. Perkins
Nokia Research Center
Communications Systems Laboratory
313 Fairchild Drive
Mountain View, CA 94303
USA
Phone: +1 650 625 2986
Email: charliep@iprg.nokia.com
Pedro M. Ruiz
University of Murcia
Dept. Information and Communications Eng.
Facultad de Informatica
Campus de Espinardo s/n, Gyeonggi-do 30100
Spain
Phone: +34 968367646
Email: pedrom@dif.um.es
Thomas Clausen
Ecole polytechnique
Project PCRI
Pole Commun de Recherche en Informatique
du plateau de Saclay
CNRS, Ecole Polytechnique, Laboratoire d'informatique 91128
France
Phone: +33 1 69 33 40 73
Email: T.Clausen@computer.org
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